Harvard Professor Reveals The BIGGEST MYTHS About Exercise & Laziness | Daniel Lieberman

Dr Daniel Lieberman 0:00 Our instincts are constantly pulling us not to exercise. I mean, our instincts are deep and they're powerful. I mean, for, for millions of years, our ancestors struggled to get enough energy to eat, right? It is a completely normal, natural instinct to want to avoid exertion, and don't ever feel bad about it. Things changed when I wrote the, um, the, the Born to Run paper in Nature, the, the, the paper that in 2004 with Dennis Bramble, where we argued that humans evolved to be long-distance runners, and we spent many years writing that paper, and the process of writing that paper got me more excited about my running, and it became like a feedback loop, and before I knew it, I was, I was doing longer distances, and, and I just got totally hooked. Now, now we study running in my, you know, y- all, all kinds of aspects of running in my lab. So it's, it's kinda like it's become a part of my life.

Dr. Rangan Chatterjee 0:49 Yeah. Well, thanks for sharing that, and that was a, and still is a seminal paper.

Dr Daniel Lieberman 0:55 Yeah.

Dr. Rangan Chatterjee 0:55 Uh, I believe you got the title from Bruce Springsteen. Is that right?

Dr Daniel Lieberman 0:59 We, we did indeed. We did indeed. And, uh, there's actually, in my, in my office, the Bruce Springsteen poster is over the door.

Dr. Rangan Chatterjee 1:06 Oh, fantastic. Well, hey, that, that resonates with me. I've got a, I've got a big CD collection of Bruce Springsteen albums in the house. I think when I was doing... I finished off my elective at the Mayo Clinic in, uh, somewhere like 2000. I was in Scottsdale in Arizona for a few weeks doing an elective, and on the way back, I was stopped off in New York, and I managed to get tickets to see Bruce in Madison Square Garden, and as a, you know, as a early 20s at the time, I think I'd died and gone to heaven. I was like, "Is this really happening?" Um, so yeah, we,

Dr. Rangan Chatterjee 1:37 we share a love for Bruce Springsteen, but you know, to get to the topic at hand, you've written a fabulous book, um, on exercise, on movement, on physical activity, and actually, I thought right at the start, we should probably define these terms because they're terms that people use interchangeably, but they can mean quite different things, can't they?

Dr Daniel Lieberman 1:58 Yeah, no, that's a good point. So physical activity is just moving, right? You know, getting up and, you know, if I were to get up and go to the bathroom, that would be physical activity of a sort, right? But, but exercise is sort of planned, voluntary physical activity for the sake of health and fitness. And, um, and so it's a kind of movement, but it's a very modern kind of movement. And I should also say, we should, we should probably also define the word exercised, right, which is why I titled the book that way, because exercised is to be anxious and nervous and harassed and, you know, concerned about something. And, you know, th- these, these words, of course, have ancient origins, but, you know, wh- when we do, you know, when we, when we do math exercises in school or, uh, you know, um, or, you know, soldiers do exercises, right? It's not, um, it's not always a good thing, right? [laughs] And I think that, that sort of ex- that sort of encapsulates the kind of ambiguity and, and, you know, and, and dual role that exercise has in our life. We, we know it's good for us, but a lot of us are really confused and anxious and harassed and concerned about it and, and really I wanted to write a book that addressed that kind of duality between physical activity and exercise and why it's such a confusing and, and complicated topic.

Dr. Rangan Chatterjee 3:07 Yeah. Um, o- one thing I find really interesting as I familiarize myself with your more recent work is this idea that y- you know, everybody listening and watching to this right now, Daniel, I'm sure is aware that physical activity is going to be beneficial in some way for them. And as a society, we're trying to move more. Uh, you know, I'm a medical doctor. You know, we're always being told that we should be encouraging our patients to move more and actually to exercise, which potentially is problematic, but it, it's interesting, isn't it, that we're moving less as humans, but we're living longer.

Dr Daniel Lieberman 3:50 Yeah.

Dr. Rangan Chatterjee 3:50 So what's going on there?

Dr Daniel Lieberman 3:51 Well, I mean, I think it's part of the, the confusion people have, right? We're told that, you know, exercise is medicine and that if you don't exercise, you'll get sick, and then they look at people like, well, I'll, I'll be very political. We, they, they look at people like Donald Trump, who, who doesn't exercise, um, and actually believes that exercise is, like, wastes your energy, right? And, um, and they see he's, you know, President of the United States in his 70s, and they wonder what's going on. And, and the answer is that, uh, you know, I think we oversimplify, um, something that is, uh, very important, which is that exercise really does improve your health. Exercise really decreases your chances of getting sick. Um, but on top of that, we have an incredible medical system, as you well know. You're a practicing physician. Um, and we're able to patch people up and keep them going and, and, um, and, you know, treat their diseases and, you know, give them pills to lower their blood pressure and other pills to lower their cholesterol and all the other sequelae, the things that result from being physically inactive, and we can keep going. Um, but, but it comes at a cost, and it comes at an increased risk and an increased vulnerability of a wide range of diseases. Just, just, you know, the data are unquestionable. 150 minutes a week of physical activity, just, you know, a brisk walk, uh, can lower your relative risk of dying at a given age by 50%. Um, that's not a, a number I just pulled out of a hat. That's a really, really, really solid number based on, on many, many, many studies. Um, but it, it's not a, it's not a magic bullet. It's not a, you know, guarantee of good health. You could still get cancer. You could still get injured, um, and, um, and vice versa. So w- we, we need to, you know, be kinda clear about what the benefits are, but also the fact that it's, this is a statistical issue, and it's a complicated issue, and there are no simple solutions to anything.

Dr. Rangan Chatterjee 5:38 So why is it when the data and the science is really clear that, as you say, 150 minutes of physical activity each week will have multiple benefits, or, or let me rephrase that, uh, may have multiple benefits on your wellbeing and your longevity, why do so many of us struggle to do that?

Dr Daniel Lieberman 5:59 Because it's, it's, it's abnormal. I mean, it's, our instincts are constantly pulling us not to exercise. I mean, our instincts are deep and they're powerful. I mean, for, for millions of years, our ancestors struggled to get enough energy to eat, right? They, every day they had to work. They didn't go crazy hard. You know, they didn't, like, work- ... eight hours a day on their feet, you know, you know, struggling to get enough food. They, they, you know, average hunter gatherers seem to work, you know, moderately hard for about two and a half hours a day, two and a quarter hours a day of, of, you know, and then light, light tasks for the rest of the day. And they, they sit as much as we do, around 9 to 10 hours a day. But, but tha- that would give them just enough food to survive. Um, you know, there, there are no obese hunter gatherers, right? And, and if they were to go for, like what I did this morning, go for a, a long run just for the hell of it in the morning, um, they would then waste all that energy, which they could use towards reproduction and the things that natural selection cares about. So nobody in the Stone Age ever went for, for a morning run for the, for the fun of it. And it's, it's a bad idea. And s- and, and, and, and, and whenever you have a chance to save energy, you, you, you should, uh, u- u- until recently. And now we live in this really strange, interesting, modern world, wonderful in all kinds of one- in regards, where we can, you know, spend our entire day without ever getting our heart rate up, you know, press buttons to get food, and shopping carts, and, and, and, you know, I don't even have to move my hand when I brush my teeth if I didn't want to. You know, I get electric toothbrush, right? I mean, everything is mechan- mechan- mechanical and, and, and the result is that we no longer have to be physically active, and we now have to do something really weird, which is to, which is to choose to be physically active. Uh, and, and although we know up here, right, in our brains that it's good for us, all kinds of instincts just kick in to tell us not to. I think the best evidence for that are when you have, like, a stairway next to an escalator, right? You must see them-

Dr. Rangan Chatterjee 7:48 Yeah

Dr Daniel Lieberman 7:48 ... you know, there are tube stops all over the place, and then, you know, s- uh, in airports, everywhere. We all, we all know this phenomenon, right? And, and it doesn't matter where you are in the world. People have studied this in Japan and in Denmark and in America and in Israel and, you know, various places. Wherever there is a stairway next to an escalator, less than 5% of people take the stairway.

Dr. Rangan Chatterjee 8:10 Wow.

Dr Daniel Lieberman 8:10 And if you put a sign up, that just goes up just a wee bit, right? If you put es- escalators in the Kalahari Desert, you know, they would take the escalator there, too. It's an instinct.

Dr. Rangan Chatterjee 8:18 Yeah. And I, and I think what you just said there about the Kalahari Desert really, I think it brings it to life for people because a lot of people feel bad. They feel guilt. They, they feel shame that they're not moving as much as either their doctor has told them, the, the news has asked them to do, or even people they're following on social media who, you know, post a photo, "Hey, just did my, uh, 10K, uh, run before breakfast. How are you all doing today?" You know, that kind of meme, which I think if you, if you find it inspiring and you're like, "Oh, well, man, I didn't do anything. I wanna do that," great. But for many people, they watch that and th- and day in, day out, they're feeding their brains with that, thinking, "I'm some kind of failure. Like, look at all these people who can move their body every day and are vibrant and are full of energy, yet just getting through the day is a real struggle." And I think that's one of the beautiful things in your book is that you, you help people not to feel bad about it. You're sort of arguing that we've not evolved to exercise.

Dr Daniel Lieberman 9:24 Absolutely. We didn't. W- look, we also didn't evolve to go to school, right? I mean, uh, we didn't... You know, u- until recently, almost nobody read, and nobody, nobody... Of course, schools didn't exist, right?

Dr. Rangan Chatterjee 9:34 Mm.

Dr Daniel Lieberman 9:34 I mean, there are so many things of our modern world that are good for us. I mean, no, no parent thinks that sending their kid to school is bad and they shouldn't, you know, learn, that their kids shouldn't learn to read. But, but, you know, that's also a modern abnormal thing. And, and h- think about how we get school to work, right? We make it compulsory. [laughs] But we also try to make it fun, too, right? You know, we have recess and all kinds of, you know, you meet your friends there, and we try to make school both fun and necessary, and I think we should treat educ- e- exercise the way we treat education. I- because it's, it's a modern abnormal thing, but it's good for us and, and, and we should, we should make it necessary, but we should also try to make it fun. But the last thing we should do is make people feel bad about it, because making people feel bad about, about doing what's natural for them, um, doesn't help anybody. And I think the same thing goes with dieting, right?

Dr. Rangan Chatterjee 10:24 Yeah.

Dr Daniel Lieberman 10:25 I mean, we never evolved to lose weight. Um, but we all, a lot of people are trying to lose weight, and for good reason, but, but when they fail on their diet, it's not because of some moral failing. It's because there are hundreds of adaptations in their bodies which wanna hold onto that fat, um, and you know, and, and, and, and, and elicit a, a kind of a, a fast, you know, an energetic crisis in their bodies to hold onto that energy, and it's not their fault that they're having a hard time-

Dr. Rangan Chatterjee 10:52 Yeah

Dr Daniel Lieberman 10:52 ... losing weight. It's, it's the fault of their, their biology, and yet we, we then blame them and make them feel bad. And I think we need to understand that our bodies aren't... We don't just get to decide what we do with our bodies. Our bodies are evolved and, uh, over millions and millions of generations, and we ha- and we need to be compassionate and understand that and work with our biology to find better solutions. I mean-

Dr. Rangan Chatterjee 11:13 Yeah

Dr Daniel Lieberman 11:13 ... what we've done with exercise is we've medicalized it. But, and I've nothing wrong with the medical profession, obviously. I, I almost became a, a physician myself, but most doctors' job is to treat people when they're sick, not to prevent them from getting sick, and that's part of the medical system as a whole. That's another issue. But, but the other thing we've done with, with, with, with exercise is we've commercialized it. We've industrialized it. We've commodified it. Uh, you know, tell people to just do it, right? And, and again, there's nothing wrong with medicalizing exercise. There's nothing wrong with commercializing and industrializing exercise. But clearly it's not enough, because, like in the United States, I don't know what the data are in England. I've been trying to find good data in England. There's not as much. But, but in the United States, only 20% of Americans actually exercise in their leisure time. That's a really staggering number, right? Um, you know, there are people who are physically active, you know, um, but, but, but not many people actually get out and do it, and there's a reason for that. It's not because they're lazy or, or bad or, or, or, or should feel guilty or ashamed. They're just being normal human beings.

Dr. Rangan Chatterjee 12:14 Yeah. You know, it, it, it really is wonderful to have someone With your pedigree, you're such an esteemed, highly respected researcher, professor. You're basically saying we need to be kind to ourselves, we need to be compassionate to ourselves. You're making the case with, you know, for physical activity and exercise that we need to be compassionate to ourselves, but I love what you said there about trying to lose weight. We've not evolved to lose weight, and what you just said, what, what you just mentioned there is a sort of central case I've been writing about over the last few months for my next book, which is on weight loss, and I, I very much agree. We have to be kind and compassionate to ourselves and understand we're kind of fighting our biology. You know, the, the environment in which we live is very much re- so removed from the environment in which we've evolved that therefore, you know, we're not doing anything necessarily wrong. We're just doing what humans have always done. Humans have always tried to make things easy, right? We've always looked for high-calorie, energy-dense foods to, so, you know, for as little energy as possible. It just so happens now that on my smartphone I can go on a shopping app and have that delivered to my house without actually moving anywhere. So i, I think it really does help people feel better. I, I read an article with you, Daniel, recently that I think you wrote in the British press, and you said in it that you were the kid who never got picked for the sports team at school, yet here we are, we're having a conversation and it's early your time. What is it, 7:30? Quarter to 8:00? Something like that?

Dr Daniel Lieberman 13:48 Uh, no, it's 8:30. It's not that early here.

Dr. Rangan Chatterjee 13:50 8:30.

Dr Daniel Lieberman 13:50 Yeah.

Dr. Rangan Chatterjee 13:50 But you've already been for a run, and that made me think about what you've just said about we've got to make it fun for people. Uh, we've got to... You know, you, we made school compulsory, but we also try and make it fun, and you're sort of making a similar case for exercise. So is part of the problem also, like with you, and o- you've obviously overcome that and you are still, uh, someone who moves regularly, but many people have that experience at school. They're not picked for the teams. They're made to feel, uh, shame and bad about themselves, that they can't be sporty like their friends who have been picked in the team, and that puts them off moving their bodies for life.

Dr Daniel Lieberman 14:30 Oh, absolutely. I mean, I, I, I, I was lucky because although I was terrible in s- I really was picked last for sports. [laughs] I, I, I, for example, played on a, on a soccer team. I g- you call it football. Um, and, uh, in, in my town that I grew up in, there was a, was a really good, good, good soccer town, and so there were kids on my team who were so much better than me. I just sat on the bench. You know? I almost never got to play because I wasn't very good. And, um, you know, I, I j- I, I felt very insecure about my body and, and, uh, but I was lucky that I had parents who loved to hike and loved to s- we went skiing in the winter, cross-country skiing, and, and my, my mother, you know, jogged and my father jogged, too. And so they were physically active, but they didn't play sports. I don't think they ever watched any sports event ever, I don't think. Um, [laughs] I played tennis a bit, but you know, that was, um... You know, I had to walk to a tennis court. That was fine, but you know, they, they weren't interested in any of that. I don't think they ever came to any game I was ever in, partly 'cause I sat on the bench, right? But, um, um, uh, so I kind of grew up thinking that it was sort of normal to be physically active but not interested in sports. But so much of physical activity that kids encounter is sports, and sports, you know, there's a whole chapter in my book on sports, sports can have exercise, but it [laughs] doesn't always have exercise, and that exercise isn't always necessarily healthy. Look at American football. I mean, that's a really profoundly unhealthy sport. Um, um, and we have more and more data, uh, to show that, not just, not just in terms of concussions, but also in terms of heart disease and other kinds of problems that, that arise from, from, you know, bulking up, making these sort of sumo wrestler-sized sort of linemen in the, in the, in the, in the sport. But, but we, you know, we, we, we, we could do a better job of making it fun. I mean, some schools do that. Um, but, um, and making sure it's about fitness. I m- m- my university, Harvard, has, um, you know, an, uh, a, a huge athletics program. We have 40 teams. Um, one of the largest athletic programs in the United States, even though this is not a powerhouse school in terms of athletics. But, um, um, but the, the, the athletics department really mostly serves the athletes on campus, and their j- job isn't really that much to get the other 80% of students, um, to be, to be physically active. And, and, and sh- surprise, surprise, the vast majority of Harvard students, about 75%, don't meet the minimum level of physical activity, um, uh, that you would need in the United States. Um, and, and that's partly because we don't make it fun for them, you know? There's no opportunities for them, and probably most of, and all of them would like to do more exercise, but they, they're busy and they're stressed and they've got courses and classes and they don't have to do it. And, and you know, we could do a much better job of helping them, uh, be active, and they want us to do a better job of helping them be active. It's not something you can just snap your fingers and do on your own.

Dr. Rangan Chatterjee 17:19 It's an interesting dilemma, isn't it, that we, we s- we, we, we, we look up to these incredible athletes, uh, with superhuman performances, you know, the American footballers, let's say, in the States, or, uh, you know, Eliud Kipchoge, the runner who can, you know, run a marathon, frankly, in a time that l- just makes me shudder even thinking about the fact that he can do [laughs] that in under two hours. But there's a difference, isn't there? It's what you're, it's the case you're sort of making, that that's kind of elite performance.

Dr. Rangan Chatterjee 17:51 It doesn't mean that's healthy. It doesn't mean that's what we should all be striving for. And, and I, I think why I find that interesting is because... Have you heard of parkrun? You familiar with parkrun?

Dr Daniel Lieberman 18:02 Yes, of course. Yeah, no, it's wonderful, parkrun. Fantastic.

Dr. Rangan Chatterjee 18:05 Yeah, but I mean, I'd love to talk about parkrun at, at some point, because there are so many aspects there, community, um, you know, uh, the social aspect to moving together, whether it's run/walk, whether it's walk, whether it's running. Um, but you also get timed at a parkrun, and I've often wondered, is timing it a good idea or not? Because loads of people who suffer with mental health problems, parkrun is actually what really, really helps them. That, that strong sense of community. You're moving. You're ... Even if you're a volunteer at that parkrun, you still get a lot of benefits. But I wonder then, when the timing comes in, and I'm not against it, I'm just sort of posing the question, does that start to make us think about performance and taking us away from just doing it because it's a fun thing to do for some of us?

Dr Daniel Lieberman 18:59 Well, I ... Yeah. I mean, I think, I think, I think we ... You know, there's so many different motivations that people have, and I think we need to, we need to, um, embrace them all, right?

Dr. Rangan Chatterjee 19:08 Yeah.

Dr Daniel Lieberman 19:08 For some people, timing is great. It gives them a little impetus. It gets them, gets them, gives them, you know, a d- you know, it helps them, you know, do a little better and, you know-

Dr. Rangan Chatterjee 19:17 Yeah

Dr Daniel Lieberman 19:17 ... challenge themselves. Other people find it defeating and then, and, and, and, and, and off-putting. And, and so I think, you know, we should let a thousand kinds of physical activity bloom, right? And if, and if, and if, you know, pa- you know, there's never gonna be one type, right?

Dr. Rangan Chatterjee 19:31 Yeah.

Dr Daniel Lieberman 19:31 For some people, why not just dancing? I mean, I, w- I have a section in the book on dancing, which is-

Dr. Rangan Chatterjee 19:36 You do, and I've got that written down to talk to you about 'cause-

Dr Daniel Lieberman 19:38 Yeah

Dr. Rangan Chatterjee 19:38 ... I didn't know that at all. So please-

Dr Daniel Lieberman 19:40 Yeah

Dr. Rangan Chatterjee 19:40 ... do expand on that.

Dr Daniel Lieberman 19:41 Yeah.

Dr. Rangan Chatterjee 19:41 It was a brilliant section.

Dr Daniel Lieberman 19:43 Yeah, I mean, every culture in the world, I, I can't find an exam- an exception, has, has not only just dancing, but endurance dancing as part of its, as part of its culture, you know? People, people dance for hours, um, in just about every culture. And even, y- even in Jane Austen, I found some wonderful quotes in, in Jane Austen, in, you know, Georgian England, where people, you know, dance the night away, right? Um, um, it's, it's, it's a way of making physical activity ... And they probably didn't think of it as exercise. It was social. It was fun. So there are many, many ways for us to get our bodies moving and to, and, and to, and get the benefits, the, the mental health benefits, the physical health benefits. And I think we should, if we're gonna be successful, we need to try to, you know, we n- there's not, not gonna be a one-size-fits-all approach, right? There's gonna have to be many approaches. I mean, look, there are some people, I, yeah, as you, as you know 'cause you read the book, throughout the book I make fun of treadmills because treadmills are, you know, for me, the apotheosis of exercise. Here's a machine, you know, you have to spend money to buy it or spend money to go to the gym to use it. It makes you work hard to basically stay in the same place. You get nothing done. It's loud. It's noisy. You know, it's, the air is fetid. I mean, I, you know, I, I put people on treadmills for a living, but I hate treadmills. I mean, I have one in my basement and I sometimes use it. So what some people do is they, they, you know, they listen to a podcast or maybe, maybe this podcast or, or they'll watch a movie or, or, or whatever to tolerate the treadmill. And, you know, if that, if that works for them, that's great. There's nothing wrong with that if ... It's actually very efficient. You can do two things at once. You can listen to a podcast and get some fy- exercise at the same time. But, but others just can't stand it. So let's, let's not be judgmental. Let's ... Any, any way that works is, is great. I mean, and we just have to support them all.

Dr. Rangan Chatterjee 21:25 I'm a big fan of individualized and personalized approaches, a- and I really like that idea that maybe we've gotta broaden out what we recommend to people. Say, you know, it doesn't matter, um, how you move your body, but you just wanna move it more, um, and find what actually works for you. But are there any sort of universal principles when it comes to movement that actually do work for all of us?

Dr Daniel Lieberman 21:53 In terms of getting us to move? I mean, I, again, I go back to the simple ... I mean, my, my, you know, I think there's two, again, two basic impetuses that have, you know, over, over millennia, have been the basis for how and why people move. And one is it, because it's necessary, and the other is because it's fun. And for most people, fun involves social. Um, um, so, uh, sometimes, you know, sometimes going for a run by yourself or a walk by yourself is meditative and it's nice to be by yourself and you can think through a problem. But for most of us, you know, we like to be with other people, and so s- that's why parkrun is so successful. It's social. Here in Cambridge, we have the November Project. Every Wednesday people do these wonderful runs, and they run up the stadium, and they do all kinds of great stuff.

Dr. Rangan Chatterjee 22:38 Wow.

Dr Daniel Lieberman 22:39 We have ... You know, all around the world there are various kinds of, of, of social events. There are ... You know, dancing is social. Um, uh, playing a game of, you know, soccer or football is social. I mean, the list goes on, right? Um, and, um, and there are many ways to do it socially, and I think ... So, so that's critical. Um, but, but that's never gonna be enough for some folks. And, and, and, you know, exercise, physical activity used to be necessary in our lives, and that was the impetus that people had to get out and, uh, you know, every day and, and do work. And so we need to find ways, without coercing them un- un- unethically, uh, to make exercise, to make physical activity necessary. And, and because it's not appropriate to tell adults that they, you can't, they can't have the benefits of society unless they exercise, right? Um, we, we need to help people help, help themselves, and I think the way to do that is through what's called a commitment contract. So let me go again back to education. In education, we ha- education works on a commitment contract basis for adults, right? So I'm a professor in a university, where people pay ghastly sums to go to Harvard, right? I mean, I think the tuition is, and, and, and room and board and all that costs like 60 to $70,000 a year. That's full, full. Of course, most students don't end up paying that. I mean, the vast majority get financial aid. So, [laughs] so don't worry. Most of my students are not fabulously wealthy. Actually, many of them are first generation students 'cause we have, we're lucky, we have really good financial aid. But anyway, somebody's paying 60 to $70,000 every year for them to go to school, and there's some commitment from them to go to school. A- a- w- and what are they doing? They're having people like me torture them, right? I make them take exams. I make them read books. I make them stay up late at night studying, and if they don't do well, I give them a bad grade, which, you know, which, you know, stigmatizes them for the rest of their life. And, and, and, um, but they do it willingly because- Because they've signed a kind of a commitment contract whereas, whereas they're paying money for me to make them do stuff which they know is good for them, which they wouldn't otherwise wouldn't do for themselves. And we do all kinds of other commitment contracts in our, in our, in our world, and, and I think exercise is, should be part of that. We should, we should find exercise, you know, there are many... So there's a wonderful program called stick.com. It's a website run through, uh, some economists. They used to be at Yale. I'm not sure if they're still at Yale, where you can basically pick either a stick, carrot or a stick, right? And, and I describe this in the book 'cause it-

Dr. Rangan Chatterjee 25:02 Yeah, you do. Yeah

Dr Daniel Lieberman 25:03 ... I found out about this 'cause there's a friend of mine in, in San Francisco who was, who has been trying to lose weight, and she, uh, gave stick.com, I think, $2,000, so not an un, not a small amount of money, and every week she agreed that she was gonna walk a certain number of miles. And if she didn't get those number- miles in, and her husband was her referee, if she didn't do those miles as affirmed by her husband, they would automatically send $50 that week to the National Rifle Association.

Dr. Rangan Chatterjee 25:32 [laughs]

Dr Daniel Lieberman 25:32 That's the big association that tries to prevent, uh, gun control laws in the United States, and she's very, very much hates the NRA and wants to see gun, gun... And she has never missed a week of her walking since she's been doing that. So she, she signed a commitment contract, put some money behind it. Now, that's a kind of an extreme one, but there are other ways we can do it, just w- through a friend. I mean, a lot of the, my early morning runs, I don't, you know, at 6:00 AM, I do not wanna run, I promise you. I mean, nobody, I wanna be in bed with my wife, right? But I often meet a friend of mine, uh, who's a cardiologist, and he's up at 6:00 AM. He doesn't wanna be there either, but we kind of agreed the day before that we were gonna meet each other at 6:00 AM, uh, to go for a run. And, uh, usually we're just, like, irritated at each other, and we don't even speak for the first, you know, 10 minutes. Um, and then slowly we warm up, and I'm never unhappy that I did that run at the end, but I, I, I did it because I f- I coerced myself through a commitment contract.

Dr. Rangan Chatterjee 26:27 Yeah. V- v- very, very practical and pragmatic approach. I guess what you're saying is that the way we've typically encouraged physical activity has been, you know, very prescriptive. You have to do this. Um, you know, if you don't do it, you're not really looking after yourself. You sort of have to rely... We, we're, we're very much putting it down to individual motivation, individual willpower, and what you're saying, I, I guess, is that this is not working, right? We've not evolved to exercise. We, we're, we're now living in a society where we simply don't have to anymore. That necessity has gone, so you need to find a way to make it necessary, and the way you've found of doing it is you're meeting someone. So if your buddy has gone to the trouble of getting up early in the morning and goes to your agreed spot, and you don't show up, there is a bit of, you know, you have social pressure to show up, which is why so many movement programs talk about, you know, doing it with other people, right? Because if you're leaving it up to yourself to motivate yourself, there's gonna be times... Like, I know when I got into Parkrun, I remember thinking at the time I wasn't really a runner, right? And we can, we can, uh... Let, let, let me put that another way. I didn't perceive myself as a runner, whereas now I do. But I still went because I did it with my son, uh, is, is reason one, and reason two is there was this big community there, this really friendly community at Parkrun. So I just had to make sure that my son and I were at the start line by 5 to 9 on a Saturday morning, and if that was, if, if I got there, I would complete a 5K. But if I had to do that myself, even if I had to do that s- myself with my son, I bet you some Saturdays we wouldn't do it. And so I think that accountability piece is, is, I think it's really interesting. Now, you, you mentioned you're

Dr. Rangan Chatterjee 28:28 not a fan of coercion, yet you write, uh, a very surprising, certainly surprising to me, you write about, is it the Swedish, uh, is it Björn Borg?

Dr Daniel Lieberman 28:39 [laughs]

Dr. Rangan Chatterjee 28:39 The, the Swedish underwear, sportswear manufacturer. And I was mesmerized reading that story. So I wonder if you could tell that, and because that's actually taking a, quite a different approach, right?

Dr Daniel Lieberman 28:50 Yeah. I had so much fun doing that. So I've, I was in, I was thinking about this, you know, 'cause I, the last section of the book, the last quarter of the book is really about how to apply the sort of natural history of exercise to the modern world. And I was interested in this idea of coercion, and I wanted to see if I could find an example of people who are forced to exercise, adults. I mean, we force kids to exercise in school, but nobody, nobody blinks an eye at that 'cause we force kids to do all kinds of stuff and think it's totally acceptable. 'Cause children can't make up their, you know, children aren't responsible for their own decisions, but adults are. And as I was, I was searching throughout the world. I was looking, I was thinking about, like, monks in Asia who are forced to do things and whatever, and I was, I wanted to... You know, I'm very into participant observation. I like to try what I study, and so, you know, that's why I've tried barefoot running, and then I've, you know, I tried it, I tried it, that's why I've chased animals on, you know, done, done races against horses and, you know, I'm, I'm into that. I like, I like-

Dr. Rangan Chatterjee 29:40 We- we- and we're gonna come to all that, believe you me. [laughs]

Dr Daniel Lieberman 29:42 Yeah. I like to put myself in the shoes of the, or the f- uh, of the, of the, of the, the people I'm studying. And, um, and so I, I found on the web a few articles about the Björn Borg company. It's a company in Sweden that makes, uh, mostly underwear, but other kinds of sports clothing. Um, it's no long- actually no longer owned by Björn Borg, but it's, um... Uh, and, and you know, it's, you know how those p- companies have those, like, little contact me thing? So I, you know, late at night I, I, I remember telling my wife I'd found this company, and I'd read some articles, and she, she said, "Well, contact them." So I, I, I, I got on the contact page, and I said, you know, "Dear Björn Borg company, I'm a, I'm a professor at, you know, whatever. I'm interested in this topic, and I'm kind of curious to learn more." And I remember going to bed and saying to her, "Yeah, I'm sure I'll never hear from them." And then the next morning in my in- inbox was an email saying, "Come and, come and join sports hour. [laughs] Come any time you want. We'll, we'd be happy to show you." [laughs] So I, uh- So I was on sabbatical and I had some time, so I got on an airplane and I went to, to, you know, uh, they were very kind and they told me when to show up. So I, I, um, I showed up, and they basically said I could talk to anybody in the company. And, you know, I had to go to sports hour 'cause at Björn Borg Company, everybody has to exercise. It's, it's, i- there's, it's a requirement. And e- there's a sports hour o- every Friday at, I think it's 10:00 AM. And, and there's no excuses, unless, unless you're injured or whatever, uh, or something like that. If you're a board member, if you're a visitor, it doesn't matter who you are. If you sweep the floors, if you're the CEO, doesn't matter. You go to sports hour. And so I, I went to sports hour, which is a really hard kind of CrossFit workout. Uh, it was great. It was exhilarating. I mean, you, you can do it as hard as you want or as light as you want. Um, and, um, and then they have all kinds of other events where they, you know, instead of a Christmas party where everybody gets drunk, they run through the streets of Stockholm and have hot chocolate afterwards, you know? I mean, it's a, it's a delightful environment. But of course, you know, not everybody liked it, and some people left the company, but some people who are in the company love it. And I just talked to folks about it and see, to see how it worked, and to my surprise, it was a, it was actually pretty popular. Um, and, um, uh, the people actually kind of realized that it was a beneficial thing. But I should also say these are people who've drunk the Kool-Aid, as we say in the United States, right? The, you know, everybody who really hated it has obviously left the company. You know, you wouldn't b- be in that company if you didn't think this was acceptable. But, um, but you know, the fact of the matter is that's, as far as I can tell, the only company in the world that does that, and we're not gonna find, you know, that's just not gonna work in most places. And we have to find other ways, uh, to make exercise necessary.

Dr. Rangan Chatterjee 32:18 Yeah. What, what's interesting about that company for me, uh, and you know, you're, you're absolutely right, there is, there's that inbuilt bias, isn't there? Because people, I guess some people, if they know that about the company and that's not their kind of thing, they may not even apply for a job in the first place. If they start working there and they think this is a good idea, but then they feel it's too much pressure, there's, you know, there, there's some sort of camara- camaraderie that they don't like or they don't thrive on, they might leave. Um, but it's an interesting model, and I appreciate this cannot be rolled out across society. There's a kind of ethical point there, I think, as well. But you know, I, I wonder what you think about the ethics of that, where a company says, "Hey, look, we..." A- and again, I'm, I'm not speaking for that company 'cause I don't know the, the ideology behind it, but let's say a company felt that, well, we know physical activity is imp- is important because it will help the employees, it will help them with their health and wellbeing, it's gonna help them concentrate, focus, be more productive. It's a great way of bonding. Um, you know, w- I, I guess what, what would happen if companies started to, some companies were like, "Well, look, this is part of the culture here, and if you wanna work here, this is sort of what we would be supporting." It's, it's quite a tricky one ethically, isn't it? Because it could be done in a way where it's very supportive and it's like, well, if you just wanna walk for that hour round the gym, that's fine. You know, there's gonna be no pressure on you from your manager or from the boss. You know, I know, I know it, it, you, you'd have to demonstrate that there was no discrimination by doing that, but it, it's working there. I mean, could that be a, could that be a s- you know, you're saying that we need to take personalized approaches.

Dr Daniel Lieberman 34:08 Well-

Dr. Rangan Chatterjee 34:09 So could that work for some companies?

Dr Daniel Lieberman 34:10 Well, I mean, let's, um, let's, uh, let's rev- let's flip the question and ask did that used to work for some companies? So, so in the United States, um, as in e- every, every, you know, in, in Europe, um, universities are kind of like companies, and every university until recently required students to exercise. Uh, in the United States physical activity, physical education was 100%, you know, every single university in the country, Harvard included, required physical education.

Dr. Rangan Chatterjee 34:36 Wow.

Dr Daniel Lieberman 34:36 Um, and, and you know, going back to, to the ancient, you know, Greek philosophers and in, you know, the traditions in India and China, everywhere in the world where you had educational systems, which of course were for elite people, right? Because, uh, peasants didn't go to, go to school, but, but, but wealthy aristocrats did. With no exception, educ- exercise became part of people's education because people understood that there was a relationship between exercise and, you know, phys- the body and the mind, right? Mental health and physical health, and that exercise is good for students. And, um, that was dropped in the United States in starting in basically in the '70s. So Harvard, for example, got rid of its physical education requirement in the 1970s. Um, and now, you know, we n- we see the, we see the results. But these are adults, you know, these are 18 plus year old people, and it was required and, um, uh, so you know, I think this... And of course, until recently, everybody had to be physically active to get to work. They had to, you know, walk to get to work. They, they didn't have elevators to get them to their floor. You know, I mean, we could go on with all the things that have changed in the world. So we've kind of shifted our, our, our, our workplace and shifted our, our schools without shifting the, the, the, the kind of how we approach our bodies. And so maybe Björn Borg Company is going back to something very ancient in a new way. Um, but um, but you know, we, the fact that we're so uncomfortable with it I think is interesting. Um, we're, we're, we're just so worried about, about, about, about coercion and people's rights and, and for good reason. Um, but we're also, um, I think, I think sometimes we, you know, we also, I'm gonna probably get myself in trouble now. Um, but look, I think it's, as you can probably tell, I'm very opposed to body shaming and fitness shaming, right?

Dr. Rangan Chatterjee 36:26 Yeah.

Dr Daniel Lieberman 36:26 It's, it's, it's unacceptable. Um, but sometimes I think because we're so worried about body shaming and fitness shaming, we, we go, we go to the extreme and basically turn off the whole system.

Dr. Rangan Chatterjee 36:39 Yeah.

Dr Daniel Lieberman 36:40 And, and I wonder if the, if, if we can't have our cake and eat it too, so to speak, right? Can we find a way to help people be physically active without engaging in body shaming, without engaging in fitness shaming? And I think we can. And again, I'm gonna go back to my commitment contract model, because if ... Let's just say you're, you're unfit, you're overweight, you're struggling, you hate to exercise, but you wanna, you wanna get, you wanna exercise. Now, if I told you I had, you had to go to a CrossFit, you know, workout every week and, you know, do 150 burpees with a, with this, you know, highly muscled, you know, you know, nutcase in front of you who's your boss, you'd, you'd hate it, right? But if you could just walk 20 minutes a day, climb the stairs, right? Pick your own goal and work towards that, you know, that would fit your, your fitness level, your, your, your, your, you know, you could do it on your own, you could do it with friends, et cetera. Not in a way that it's ... We can find ways for people to be more physically active that can, can accommodate every disability, can accommodate every level of fitness, can accommodate-

Dr. Rangan Chatterjee 37:45 Yeah

Dr Daniel Lieberman 37:45 ... you know. But, but we, we, as a society we've been very uncreative about it, where, where we're, um, we're not really willing to put in the time and the money and the effort to make it happen.

Dr. Rangan Chatterjee 37:56 Yeah. And I, I think a lot of people get put off by gyms, for example. They've, they've sort of been sold this idea that gyms, if I want to get fit, whatever their interpretation of fit is, you know, I wanna-

Dr Daniel Lieberman 38:07 [clears throat]

Dr. Rangan Chatterjee 38:08 ... I wanna do my physical activity, then it has to be at the gym. It has to have a particular name, it has to have particular clothes that I wear, because if I don't, it doesn't count. And I, for me as a doctor, I find myself trying to break down that barrier with patients all the time. I've often said ... Now, I didn't know about the, these sort of tribes and these cultures for years who've danced, but I've often said to, to patients, said, "Look, do you like dancing?" They go, "Yeah, I like dancing." I said, "Okay. Well, well, let's start there. Why not, you know, just before dinner every night for 10 minutes have a dance in the kitchen, put on the tunes and dance?" Go, "Yeah, but do I need something more?" I said, "Well, let's start there." And I've seen e- I've seen families bond over it, I've seen people's mood get better just from the act of dancing every day. And, you know, a lot of people are conditioned to think, "Oh, no, it needs to have ... You know, I, I need to go to this particular class, and then I need to buy the latest outfit." And it's-

Dr Daniel Lieberman 39:04 Well, again, that's the commodification, commercialization of exercise, right? It's, if it's, it's, uh, it's now a product and you have to spend money on it, and, you know, you, you have to, uh, you know, and there's some- there's people there to, to, to, to advertise to us that, you know, you can't run unless you wear these fancy shoes and you, you have to have your fancy watch and all this sort of stuff. And frankly, I, I enjoy fancy shoes and my fancy watch when I go running, but we don't need it actually.

Dr. Rangan Chatterjee 39:29 Yeah.

Dr Daniel Lieberman 39:29 Um, and, and, and it works for some people, but it obviously is not working for the, for, for everybody. And so yeah, again, I think we need to, we need to kind of r- step back from our Western medicalized, commercialized attitude towards exercise and take a broader view, a broader perspective. And if we just simply do that, which is what my book tries to do, we'll, we'll, we'll come up with all kinds of other wonderful solutions. Dancing is just one of them. Going for, going for walks with your, your, your f- Like, why, for example, do we have so many boring meetings where we sit around in chairs or now we-

Dr. Rangan Chatterjee 40:03 Yeah

Dr Daniel Lieberman 40:03 ... sit glued to our bloody Zoom screens, right? Why can't we, can't we get up and walk, right? And have meetings on, on the hoof, right? Um-

Dr. Rangan Chatterjee 40:12 Yeah

Dr Daniel Lieberman 40:12 ... there's so many examples of ways in which we could, we could, we could just, uh, encourage physical activity in a way that'll make it both necessary and fun.

Dr. Rangan Chatterjee 40:22 Yeah. Now, now Daniel, a lot of the research you, you did for this book has, has taken you to wonderful places around the world to do what sound like from, from where I'm sitting incredible things. You know, uh, in Tanzania, you know, you've, you've stayed with hunter gatherer tribes, you've I think hunted kudu, you've ran with horses and I'd love to sort of explore some of those because these are things that many of us have never done, and I think there's something to be, to be learnt from that. So I was gonna ask you what has been some of the most surprising things that you've learnt when you've gone and lived alongside indigenous tribes and, and communities? You've mentioned dancing. Did that surprise you, and was there anything else that you discovered that you didn't previously know?

Dr Daniel Lieberman 41:12 Well, I mean, I, I'm a really lucky person. I have a, I'm such a, you know, fortunate to have a great job that, you know, I get paid to go have fun and travel around the world and study things that interest me. I'm, I'm a, I'm a ridiculously lucky person. And, um, I would say that, um, you know, what surprised me the most is really, I mean, quite literally it's the story I tell in the beginning of the book, which is, um, so, uh, so which is that n- people in these, in these societies don't think what they're doing is exercise. And for me, that was the, that was the, that was the spark that started this book, 'cause I, it was 2012 and I was finishing my previous book, which is called The Story of the Human Body, and, and in that book, the kind of message of that book is we didn't evolve to be healthy. And that book is about mismatched diseases, how the, how, you know, the modern world that we're living is we're, we're poorly adapted to it in some respects that makes it get us sick in various ways. But, um, um, so I was finishing up that book and I went to Highland Mex- So I went to the, the Ironman competition in, in Kona. Um, uh, this is a true story. I, I'm not exaggerating anything here. It was, I was part of the medical conference at, at, at, uh, that precedes the, this incredible race, which is just amazing. You know, people do a 2.4 mile open water swim, then they do 112 mile bicycle ride across the desert, and then they do a full marathon in, like, 90 degree heat. It's insane, right? And, and [laughs] the people who win, like, do it in, like, a little over eight hours. I mean, they're, they're like cyborgs. They're not real human beings. Like, you know, they're ... It's just in- it's, it's astonishing. And then I got back- ... you know, working on the book, r- and then went to Highland Mexico, where I hired a guy to help me, um, go to really, really remote areas to study the Tarahumara who are so famous for their running. And, um, um, and, you know, I'd read about how they barefoot run and do these long distances, and what I discovered was that, first of all, I didn't see anybody running barefoot whatsoever anywhere, and I was traveling all over the place. And, and, um, when I asked people about their running, they were like, "Well, people did run in these traditional races. Um, but other than that, they didn't run." And I had this, like, list of questions, being a good anthropologist. I had a, I had a questionnaire, which I had, you know, designed carefully, and one of the questions was, you know, how do you train for your running? And my translator couldn't, you know, was struggling to figure out how to t- ask this question because there was no word for, for train in the Native American language, Raramuri. And so she was trying to, you know, you practice, you know, she was s- trying to explain to these... And, and there was this one 70-something-year-old guy she asked, and I remember him because he was really, he was really, uh, he was, I don't know, maybe the 10th or 12th person I was, I sort of was measuring and studying, and, and he was kind of very serious fellow. Um, he was w- he was a runner, too, by the way. Um, and, and the vast majority of people don't run very much. Um, he was a runner and, and, uh, he, through the translator, asked me, "W- why would anybody run if they didn't have to?" And he, uh, and at first, I was thinking, "Ugh, this question I wrote is really bad." [laughs] I mean, I wr- I wrote the wrong question. And then I realized, actually, this is telling me something. That, that, that, that, you know, people there run when they need to and they w- but the word exercise is just not part of their, their lexicon, you know? Um, training is not part of their lexicon. And, uh, that kind of just permeated my brain as I started, you know, I took every opportunity I could to, to do something where I, you know, I was in, I was in the Western Ghats. We were looking for barefoot runners, and we were, you know, looking for people who were r- running there. We were, you know, been into Greenland and to various places in Africa, et cetera. You know, every place I've gone, I've noticed that people who are very physically active don't think of what they do in any way whatsoever as exercise. Um, and to me, I think that's been most surprising. Uh, that was initially most surprising.

Dr. Rangan Chatterjee 45:05 Yeah. I mean, it's very powerful, even though I've read that, to hear you explain it is very, very powerful because it gets to the heart of what the problem in society is about getting us to move more, right? It's, it's like these, the- these communities don't have words for exercise or training. It just doesn't exist because it's, I guess, it's necessity-driven.

Dr Daniel Lieberman 45:29 Or it's, or, or, you know what's really beautiful? The Tarahumara, when they run their long distance races, it's a form of prayer for them. I mean, that's, to me, that's really beautiful. It's spiritual, right? They run because they believe it makes them closer to God.

Dr. Rangan Chatterjee 45:43 Yes.

Dr Daniel Lieberman 45:43 Um, what if we [laughs] adopted that attitude, right? I mean, it's such a beautiful thought, right? And it, and it, and, um, and, and it does, right? And for them, actually, the, the concept of cha- actually, I have one of the balls over here, actually.

Dr. Rangan Chatterjee 45:56 [laughs]

Dr Daniel Lieberman 45:57 This is one of the, the balls they use in their, in their foot race. Um, and, um, when they chase this ball, the, the ball gets dirty, et cetera, and it gets lost, and for them, the, kind of the randomness is like a metaphor for, for life and for the vagaries of life, and, and it's, it's really beautiful what they do. And, and, and that's true of, of, of the, a lot of the sacred dances that people do, and, and the list goes on. It, it-

Dr. Rangan Chatterjee 46:22 W- would, would they kick that ball around and follow it? Is that what would happen? Someone would-

Dr Daniel Lieberman 46:25 Yeah, they kind of flick it with their foot, and it, as far as they can, and then they chase it, and they find it again, and they flick it, and they chase it, and they find it, and they flick it. And they'll do this, there are two teams doing this, and they'll do it until one team laps the other in a, in a course.

Dr. Rangan Chatterjee 46:39 Yeah.

Dr Daniel Lieberman 46:39 And sometimes the race can be 10 miles, and sometimes the race can be 50 miles, and, and, you know, it depends on how they set up the race and what they agree on beforehand. Um, but th- and, and they're betting wildly, so you know, they're, it's a big social event, and, and it's fun. It's, it's, but it's also a form of prayer.

Dr. Rangan Chatterjee 46:56 Yeah. This is something I explored in a, in a conversation, uh, with Sanjay Rawal, I don't know how many episodes ago, who, he was the director on a film called 3100. Um, if you've not seen it-

Dr Daniel Lieberman 47:07 I, I, I've s- I've seen snippets of it, but I haven't, I've not had a chance to sit down and watch the whole thing, but it's amazing

Dr. Rangan Chatterjee 47:12 Having, having, having read your book, I think y- I can almost guarantee you would love this documentary-

Dr Daniel Lieberman 47:16 Yeah

Dr. Rangan Chatterjee 47:16 ... because it, it's really, in many ways, showing tribes around the world how running is, you know, it is about transcendence. It's a spiritual practice. It's not for calories burned, how many miles have I gone, you know, uh, what did my heart rate do? All this kind of stuff that, again, nothing necessarily wrong with it. It's, it's to get them closer to, you know, I guess being at one with the world, sort of finding themselves, and it i- it's

Dr. Rangan Chatterjee 47:47 really, really interesting that, because the way we do it here in the West, by and large, and of course everyone is different, does seem to be quite far removed from that. Um, it's interesting because y- you have been termed the barefoot professor in the past. Um, and you mentioned when you went to Mexico, you didn't see that many people barefoot. I think you've been to other cultures like in Kenya and India where you have seen a lot of people barefoot. So what's the deal there?

Dr Daniel Lieberman 48:17 Well, there's a story behind it, if you don't, if I have time. But-

Dr. Rangan Chatterjee 48:19 I've, I've got plenty of time, and this is probably one of the mo- the things I'm most interested in, so, and I've got-

Dr Daniel Lieberman 48:24 Yes

Dr. Rangan Chatterjee 48:24 ... the sort of professor of barefoot running in front of me, so you go-

Dr Daniel Lieberman 48:28 So here's the story

Dr. Rangan Chatterjee 48:28 ... as deep as you want here.

Dr Daniel Lieberman 48:29 So here's the story. So in 2004, Dennis Bramble and I published a Born to Run paper. Um, yeah, w- that was the title in, in Nature, Born to Run. And, and, um, and I, it was fun. I got invited to give all kinds of lectures, and I gave a lecture, uh, the night before the Boston Marathon, I think it was 2005, and it was a dark and stormy night, literally. I mean, there was a incredible rainstorm that came in the, just before the marathon. Everyone was worried about, you know, the rain and all that. And it was a packed audience, and there was a guy sitting in the front row who I never, I'll never forget him, 'cause I remember he looked kind of like a bum, uh, from Harvard Square, and he had, like, his, he had socks on that were wrapped in duct tape And he was very intent on the lecture, and afterwards he, uh, came up to me and asked, "You know, if people evolved to run, um, um, um, you know, w- w- did they run barefoot, and is there any problem with that?" And I said, "Well, of course they ran barefoot because shoes were invented fairly recently," and, um, and, you know, I don't know really very much about barefoot running. Um, but, you know ... And he, I started ... And I realized he ... So at the time we were studying head stabilization. Now, when you run, when, when your body hits the ground, your head jiggles, right? And we were interested in how the body stabilizes the head, you know, how you prevent that jiggling from occurring so it doesn't blur your vision. And most of the runners we were looking at were heel strikers, right? They would land on their heel, and their head would jiggle. And I remember there was a few runners occasionally would come into the lab, and they would be forefoot strikers. They'd land on the ball of their foot, and their head wouldn't jiggle as much. And I remember thinking, "Argh," they were, like, you know, ruining my experiment and, you know-

Dr. Rangan Chatterjee 50:01 [laughs]

Dr Daniel Lieberman 50:02 ... 'cause, you know, we're not getting the head jiggling we wanted to s- to measure. And, um, so this guy comes in, and, uh, his name is Barefoot Jeffrey, um, and, uh, he runs a, he owns a bicycle shop here in the area. And he came in, and we set up, you know, the equipment, and he just ran light as a feather. Now, no head jiggling whatsoever [laughs] . And, and, you know, he landed on the ball of his foot, and I asked him why he landed on the ball of his foot, and he said, "Well, it doesn't hurt. Uh, if you land on your heel, it hurts." And so we started doing some experiments and realized that that's how people ran when they're barefoot. They, they ... You can't slam into the ground like you can in a shoe 'cause you have all that cushioning in the shoe. You have to run lightly and gently. And so we got to studying barefoot running, and, of course, I, I've been working in Africa for, for, for many decades, and I'd seen people in Africa, you know, running barefoot, but I'd never really measured them. So we went out and started measuring them and, you know, published a, a s- another paper in Nature with a, about the biomechanics of barefoot running. But I always like to try what I study, and we realized that, that, uh, to me it's not about whether you're barefoot or not. To me, it's about how you run. To me, running is a skill just like swimming or climbing a tree or all many other things that we do, and there are better and worse ways to run. And, and, um, and what barefoot running does is that it helps us, uh, learn the skill of running, that I think, I think there are advantages to not crashing into the ground and relying on some technology in your shoe to make that, uh, comfortable. And so to me it's not about, you know ... To me, I think, you know, you can run beautifully in shoes, and you can run terribly in shoes, and you can run beautifully barefoot, and you can run terribly barefoot. But, um, what really matters is how you run, and that barefoot running gives us information. And, and sure, shoes are comfortable, and I, I mostly wear shoes when I run. I also wear minimal shoes, and I also agree with everything you just said. You can't just throw away your shoes or transition your shoes and, and, and, and immediately change your gait. You have to transition gradually and slowly, and you have to learn the skill of running. But if you do, the evidence suggests that there's a lot of benefits, and you don't destroy your knees, and you can, you can do all kinds of good things with your body. And, and, um, and, you know, there's a lot of evidence, and there's mounting evidence, I think, that, that supports that. But it's, of course, it's still controversial because there's a lot of money in the, in the, in the, in the, in the, you know, be it in the shoe industry, and, and, and there are people who like what they do, and they get upset if you tell them that, you know, they should be doing something different. And, you know, for many of them, they, they shouldn't. You know, if it ain't broke, don't, don't fix it. But, but many people are injured, and m- they might benefit from changing the way they run.

Dr. Rangan Chatterjee 52:33 Yeah. I mean, that certainly echoes what I've seen in my clinical experience, and even a really good friend of mine actually who has very much been enamored with my journey to minimalist shoes, he sort of transitioned to pretty much everything apart from running until maybe six months ago. He, you know, he'd wear minimalist shoes for work, for walking, for going out with his family at the weekends, and he really liked the connection it gave him, and he, he sort of felt it was, he was moving differently. But he said, "I've got no real reason to change the way I run because I can do it, you know, I, I don't get injured." But something changed about six months ago, I think, just on that journey. He was quite interested to go, "Well, what is it like if I actually try running?" So he went super slow. You know, he could only do 3 or 4K, I think, initially. But now he's a, you know, he's, he's a badge-wearing sort of barefoot runner, and I think, I think all these things become quite reductionist, don't they? It's like barefoot running, good or bad.

Dr Daniel Lieberman 53:35 Yeah.

Dr. Rangan Chatterjee 53:35 You know, minimal shoes, good or bad. It's like, well, it kinda depends on the context a little bit, doesn't it?

Dr Daniel Lieberman 53:40 Yeah, absolutely. And, and, uh, you know, almost all the world's g- best runners are, have what I call a barefoot style. Um, and yet it's funny that there's some people who get really mad, like, you know, like, "You're telling me I have to be a forefoot striker." It's like, "No, you don't have to be a forefoot striker." Um, but, you know, some of the world's best runners are forefoot strikers. You might ... You know, there's nothing wrong with it [laughs] . So people are very, um, it, it ... People are tribal, right? Just like in the United States, you know, you've got the Republicans versus Democrats. Well, you now have forefoot strikers versus rearfoot strikers. It's crazy. Um-

Dr. Rangan Chatterjee 54:11 Yeah

Dr Daniel Lieberman 54:11 ... um, I mean, uh, I think actually, uh, it's interesting, people often ask me what kind of shoes I wear. Well, I wear many different kinds of shoes. You know, today I wore one pair, but tomorrow I'll probably wear something other. Maybe Thursday I'll, I'll go barefoot. I mean, you know, uh, w- why do we have to categorize ourselves and just do one thing? Um, it's, it's a fascinating, um, fascinating insight. The other thing that's interesting to me about barefoot running is how out of touch we are with our bodies. A lot of people, they just, the idea just makes them cringe, like, "Are you serious? I mean, well, you, like, you're gonna cut your feet. What about all the hypodermic needles and glass out there?" And, you know, I've heard it all, right? And, and, and, and, and all these people haven't tried. They have no idea. And, you know, I think everybody should just try. Just, you know, go for a few hundred meters. Take your shoes off and run for just a few hundred meters down a, a, a street. Don't, don't ... You know, make sure it's a smooth street, and, you know, don't do it at night, so you can see the glass and the hypodermic needles, depending on where you live, right? But you'll discover that it's actually kind of fun. Um, but don't do too much too fast 'cause you will injure yourself. If you do too, too much too fast. But, but people are just out of touch with how their bodies work

Dr. Rangan Chatterjee 55:18 I guess even just if people are lucky enough to have a garden or a backyard, you know, even just start by walking in your backyard or garden and just get used to that feeling again. You know, s- I, I've always, I'll tell you what, I've always, it's always fascinated me. So I, you know, my parents are immigrants from India to the UK. My dad came over in the early 1960s. And, you know, in Asian culture, certainly in Indian culture, you don't wear shoes inside the house, right? It's just, it's just not done. So I grew up, we never wore shoes inside the house. We'd always leave it outside or in the porch. Then you'd go in either in your socks or barefoots. And it's only, you know, when you get older and you start interacting with your friends and go around to their houses, you go... I remember thinking, "Oh, well, these guys wear shoes in their house. Oh, oh, wow." You know, 'cause my norm was that you don't wear shoes in your house. And it, it's just interesting how culturally things are different. I'm, I'm not saying that necessarily plays out as we get older, but it is interesting that I've certainly noticed in some of my, uh, some of my friends growing up, um, uh, one of my best mates in particular, I remember he, you know, even at university going round, he'd always, like, getting ready in the morning, having a shower, shaving, would be putting his shoes on even if he was inside the house. And I guess culturally these things are different. I remember going to India every other summer when I was a kid. We used to go to, uh, a city called Kolkata or what used to be called Calcutta for six weeks. Um, and I remember my, playing with my cousins, and my, my cousin, who's about four years younger than me, he'd always want me to come and play football. And we'd go down to the, to the apartment. Uh, just underneath all the apartments there was a bit of, a bit of land, and they were all playing barefoot, like properly tackling, uh, you know, going in hard. And I started playing and I found it really difficult at first, but by the end of the summer you're used to it. So-

Dr Daniel Lieberman 57:09 Sure

Dr. Rangan Chatterjee 57:09 ... it's, it's different everywhere, right? In terms of how much they-

Dr Daniel Lieberman 57:12 Right

Dr. Rangan Chatterjee 57:13 ... actually wear shoes.

Dr Daniel Lieberman 57:14 Right. Yeah. I, I mean, I've also had those experiences. Uh, I don't, obviously haven't gone to India as much as you have, but I've had those experiences and actually one of my favorite, uh, moments in, was playing, um, I didn't, didn't make it into the book, but I remember playing cricket with a bunch of kids in, in, in a, in a tiny little village in the, in the Ghat Mountains. Um, and what was terrifying was not being barefoot, it was those bowlers. Boy, they, um, they were terrifying. But, but, but the way in which we... But you used a very important term there, which is this cultural, these cultural ideals, and they ex- they, they translate into so many other ways in which we use our bodies. So another example is sitting or ano- or sleeping, right? The idea that, that it's, you know, that this, one of the Western ideas we have is that you should sleep in a s- in a quiet, dark room with a soft, comfortable mattress, with nobody around you, and no sound, and no light, and no nothing, in this kind of, you know, um, stimulus-free environment. Um, that's a cultural norm too, right? And un- till recently, even in the West, people, nobody did that, right? And, and, and yet people feel that they can't sleep properly unless they're in that kind of environment. Which is, which is, again, it's a, it's what you get used to. It's a cultural norm. And then, and then if you're not in that kind of environment, then you get, uh, you get stressed and your cortisol levels go up because you're, you're anxious about sleep, and of course, that prevents you from sleeping in the first place. Or how we sit, right? We're told, you know, we have to sit in a chair with a, you know, particular posture. That's also a cultural norm. That's completely made up in the 19th century by German orthopedic surgeons who, who for some reason opined that when you sit, you should have the same curvature in your spine as when you stand. There's no evidence to support that whatsoever. It's completely made up. And in fact, there's plenty of evidence that it, that, that doesn't support that. I could go on. We have all kinds of cultural norms that we... There's nothing wrong with them, 'cause you can't not have a culture. I mean, we all grew up in a particular culture. But sometimes we need to step back from what we're told and question it or ask, you know, "Does that work for me?" Uh, particularly in our modern world in which, which, uh, often it doesn't.

Dr. Rangan Chatterjee 59:11 Yeah. S- so, so fascinating. Well, let, let's go into some of these norms or myths. Like, you, you, you sort of bust quite a lot of myths in this book. Um, we've mentioned running a bit, so let, let's go in there. Running, you know, even within the medical profession, people will say that running is bad for your knees. I'd love-

Dr Daniel Lieberman 59:33 Poppycock

Dr. Rangan Chatterjee 59:33 ... you to expand.

Dr Daniel Lieberman 59:34 [laughs]

Dr. Rangan Chatterjee 59:35 Poppycock, okay.

Dr Daniel Lieberman 59:36 Um, I don't know if I'm allowed to say that. Um, but, um, uh, look, running injuries are, are common, right? I mean, when people do any exercise, they'll injure themselves, and running is a, it can be very repetitive, right? You know, you do thousands and thousands and thousands of steps with high forces, and yes, people do injure themselves, and yes, the knee is the most common site of injury. But we already talked about this, that I think running is a skill and if you actually learn to run properly, uh, the, the, the forces and the... We actually know from a biomechanical level as well as even epidemiologically that proper running form can decrease the rate of knee injury. But the, but the chestnut of all those injuries, of the myths, is the idea that running causes arthritis of the knee. We've actually done a lot of research on arthritis in my lab, and the evolution of arthritis. Turns out, by the way, that your chances of getting arthritis for a given year in your age have doubled since World War II. Doubled, right?

Dr. Rangan Chatterjee 1:00:27 Wow.

Dr Daniel Lieberman 1:00:27 And that's clearly s- 'cause, not 'cause genes for arthritis have swept through the population, it's 'cause our, our lifestyle has changed, and we're trying to figure out what that's, what that's about. And it's not being, not, not, not about being more [laughs] physically active 'cause people have become less physically active today. And it turns out that running is actually heal- uh, actually healthy for your knees. It actually, it's good for cartilage, uh, growth. Um, it actually keeps the cartilage healthy as you get, as you, as you age, physical activity does. So, and there have been maybe 15 randomized control studies showing that runners do not have a higher incidence of knee arthritis, and yet I can't tell you how many physicians I've told, uh, spoke to who just assume that with no evidence.

Dr. Rangan Chatterjee 1:01:04 Yeah.

Dr Daniel Lieberman 1:01:04 Zilch. They just say it because it's a, it's a, it's a cultural bias, and then they have the authority of being a physician, but they're wrong. It's just, it's just flat out wrong and it can be disproved. Um, so I don't-

Dr. Rangan Chatterjee 1:01:15 And the problem is, can I say, one of the-

Dr Daniel Lieberman 1:01:17 Yeah

Dr. Rangan Chatterjee 1:01:17 ... one of the problems is, there's a wider problem here, I think, which is- We're so far removed from our evolutionary heritage or, you know, evolutionary norms compared to these modern societal cultural norms that I think we become very... We're so risk-averse when it comes to physical activity. You know, any time we talk about it, we have to give disclaimers. We have to say, "Yes, be careful when you do that." Like, every time I submit a book manuscript, the editors come out, "You know, just make sure that people aren't gonna get injured, and do this." And, and I understand it, because of course no one wants to get injured, but w- we made something that is fundamentally part of our, our human nature to move our bodies. We turn it into something that's quite removed from us. We have to be careful. We need to, you know, we need to keep our back like this, we need... And, and again, please, I'm not trying to say that those things don't have merit for some people. I just really feel very much like you said, we've commoditized it. We've made it feel like it's this thing that's separate from the rest of our lives, and I think that's really problematic.

Dr Daniel Lieberman 1:02:23 Well, another example is sleep. I mean, one of the things, I... So when I wrote this book, I thought, "If I'm gonna do a natural history of physical activity, I better start with physical inactivity," 'cause after all, it's two sides of the same coin. And I've been very interested in sitting for a while, and I've studied sitting for a while, but I didn't really know... I'd not really delved into the sleep literature. And I was astonished as I started looking at the sleep literature, that this idea that you need eight hours is, is also just made up, as far as I can tell. There's, there's actually n- no empirical evidence [laughs] for it. Um, I mean, some people do need eight hours, but it's, it's been oversimplified and over-commodified, and, and, and in- and imbued with kind of cultural significance. So when, turns out when we look at people in parts of the world who don't have electricity, they don't have internet, they don't have iPhones, they don't have, you know, telephones, they don't have anything that has electricity, right? They don't sleep eight hours. They actually sleep between 5.9 and 7.1 hours, I think. That's the... I can't remember the exact numbers, right? Um, and um, uh, and furthermore, when you look at epidemiological studies of very large samples of people, the op- you know, in terms of relative risk of heart disease and various other, other, other, you know, illnesses, the optimum always comes out to seven, not eight. I mean, of course, there are some people out there, 'cause there's variation around the mean, who do benefit from eight, but there's some people who get by at six. But somehow we've, we've turned eight into this kind of, this, this ideal. And then what happens is that people feel like, "Oh my gosh, I'm not getting eight hours of sleep. There's something wrong with me." Then they get anxious. And of course, when you get anxious, you, you produce cortisol, which makes you stressed, and cortisol is the enemy of sleep. And we create this, we create this kind of feedback loop, which then gets people to go buy drugs to make them sleep, or spend ridiculous amounts of money on some, you know, clip on their nose that helps them sleep or, you know, whatever it is, you know. Curtains or new mattress or whatever. And you know, none of that, you know, we've created a sleep industrial complex based on a, on a cultural norm that's kind of Western and modern, but not necessarily rooted in our biology.

Dr. Rangan Chatterjee 1:04:24 Yeah. And I, and I guess it's one of the problems, really, one of your central arguments is that it's n- there's no one size fits all, right? We're all different. We all have to find what works for us, what's gonna get us moving. I guess, what's gonna get us sleeping. And some of us, I guess, you know, I would just add from a, from a clinician perspective, that I, I found that you can't really make these hard and fast rules for people, because the individual in front of me, there are so many other inputs going on into their life. So what are their stress levels like? What has been their state of health for five years? What, what else is going on? And therefore, their sleep requirement is gonna depend on all those things. Whereas some of these communities, let's say, without electricity, without iPhones, um, maybe, uh, I'm just hypothesizing here, maybe their stress levels are really, really low. Maybe they're... Actually, maybe they can get by with less sleep than someone who has huge amounts of stress. I, you know, I, obviously, I c- I can't say the answer to that. I'm just hypothesizing. But it is quite individual, right? And, um-

Dr Daniel Lieberman 1:05:29 Of course. Of course, yeah

Dr. Rangan Chatterjee 1:05:30 ... and, and we sort of miss that.

Dr Daniel Lieberman 1:05:32 Yeah.

Dr. Rangan Chatterjee 1:05:32 So sleep, there's a myth there. Running is, uh, good for the knees. Of course, if someone... So, so I'm just, just trying to play devil's advocate. If someone listening to that goes, "Okay, I, I hear what you're saying, Professor Lieberman, but every time I run I get knee pain. So what should I do then?"

Dr Daniel Lieberman 1:05:51 Well, I mean, um, well, there's two possibilities. One is you should back off, 'cause pain is a, is a, is a adaptation. It tells you if something's wrong, right? And, and you shouldn't ignore pain. And if, and if you have pain, you have to either, you can either treat the cause or you can treat the symptoms. So the question is, what's causing that pain? And one possibility is you do already have damage in your knee, in which case running will exacerbate it, right? If you already have arthritis in your knee, running is not a good idea because it's gonna, it's gonna exacerbate it. But the other possibility is that the way in which you're running is causing you to get the knee pain in the first place, and, and maybe you should s- instead of... And you know, so many people go to a sports medicine doctor, right, who will look at their knee, but never look at how they run.

Dr. Rangan Chatterjee 1:06:30 Yeah.

Dr Daniel Lieberman 1:06:31 Right? They're treating the symptom rather than the cause. Now, you know, these are things, there's no one answer to it, and it's, I'm not saying that, you know, barefoot running is gonna solve everybody's running problems. Um, but, uh, but you might wanna look at how you run, and it might be that there's a better way for you to run that might actually alleviate, um, the repetitive stresses that you're putting on the tissues around your knee that might be causing the running pain. But you know, it's, uh, there's no one-size-fits, fits all answer.

Dr. Rangan Chatterjee 1:06:57 Yeah. It's, it is a scale, and I think maybe... I'd be interested to see what happens with kids. Like, my kids have never really worn cushioned shoes, like from a young age, particularly my daughter, they've gone straight to minimalist shoes. So I don't know if you would make a... Of course, they're not necessarily learning the skill of running, but they're also not wearing cushioned shoes to start them changing their gait accordingly. So I don't know, have you got any research as to what might happen to those kids who've never worn cushioned shoes in the first place?

Dr Daniel Lieberman 1:07:28 Well, we've been studying that in Africa for ages, right? So we've, we've got lots of data. We've published many s- many papers on, on kids who've grown up never wearing shoes and comparing them to kids from the same tribe who do wear shoes. And what we've not done, and what's really hard to do, is a randomized control study where you, where you randomize people into wearing shoes and not wearing shoes. As you can imagine, that's [laughs] a challenging study to do, especially in a place like Boston where it gets very cold winters. Um, but, um, but yeah, we've ... You know, my lab, we've published lots of papers. Like we have a paper coming out I think today in, in, uh, in, uh, Nature Scientific Reviews on, on, um, on toe springs, that cur- upward curvature in almost every shoe that exists on the planet, including many minimal shoes, and how that changes the biomechanics of the foot. So we're, we're very interested in how shoes affect foot function, and then how that affects how we walk and how we run. We had a paper last year in Nature which showed, um, that, about how calluses work, um, how calluses protect the foot, but, but how they, uh, transmit all the f- the f- the, the, the sensory information from the ground to the body. So unlike a shoe, which is a trade-off between protection and, and sensory information, calluses don't have that trade-off, which is really interesting. But, uh, so yeah, this is a, a subject of, of, of intense research in my lab. We-

Dr. Rangan Chatterjee 1:08:39 So, so, so removing calluses, uh, as is a modern trend to do for cosmetic reasons, could be problematic. You're saying that calluses-

Dr Daniel Lieberman 1:08:48 Well-

Dr. Rangan Chatterjee 1:08:48 ... actually give us that sensory information that we need.

Dr Daniel Lieberman 1:08:52 Yeah. Well, calluses also come from just ... You know, calluses come from being barefoot, right? When the, the friction and the pressure of being barefoot, you grow calluses, right? And so most of us who wear shoes have very thin calluses, but people who are barefoot have thick calluses. And it turns out that thick calluses, I, I learned this when, when being barefoot, which is that, you know, I would step on something and I'd still feel it just as well, you know, as, as, uh, after my calluses had grown than when I, you know ... 'Cause e- every winter, of course, I'm wearing shoes, and then I often take my shoes off in the spring after the Boston Marathon, and I sort of slowly regrow my calluses. And I noticed that as the s- as the spring and the summer went on, I would step on the same pebble or a similar pebble, and I would feel the pebble just as much, but it didn't hurt. So it wasn't that I was losing sensory information, I was just getting more protection. And so we, we, that started a project to kind of to study how calluses work. 'Cause after all, you know, until recently, everybody that was their ... We didn't have shoes, we just had calluses. And, and my dog, you know, she goes barefoot all the time. Um, I, one of my favorite moments was, uh, I was running barefoot, uh, a few, few blocks from my house. There's a woman I see all, every morning, you know, or many mornings, walking her two just two beautiful dogs. And I remember one morning I was s- running by her on my way to the river here, and she said, "You're, you're barefoot." And, and I said to her as I whizzed by, "Your dogs are barefoot."

Dr. Rangan Chatterjee 1:10:14 [laughs]

Dr Daniel Lieberman 1:10:15 And the look of shock on her face, like, oh my gosh, my dogs are barefoot. But, you know, the dogs don't mind, right? And our, our ancestors didn't mind. Uh, people in all over the world don't mind. I'm not saying that shoes are bad or whatever, we shouldn't wear shoes, but you know, shoes change how, how our bodies work. And, and, and, and there's nothing, you know, judgmental about it, nothing wrong with wearing shoes. There's nothing virtuous about being barefoot. Um, but we, you know, we learn something about how biology works by, by studying people unlike us.

Dr. Rangan Chatterjee 1:10:45 Yeah. Super, super interesting. Couple more myths I'd just like to go through before we wrap up, Daniel. Um, you mentioned early on in our conversation that hunter-gatherers sit down for long periods of time.

Dr Daniel Lieberman 1:10:59 [laughs]

Dr. Rangan Chatterjee 1:11:00 So there's, there's this idea that sitting is really bad for us. Um, what would you say to that?

Dr Daniel Lieberman 1:11:06 Well, I mean, you know, w- we, again, oversimplify things, right? So you and I are sitting, um, while we're having this conversation, and, uh, sitting is the new smoking, so we might as well just be smoking a pack of cigarettes, right? And it is true that people who are physically inactive do, do run into trouble, but um, but it turns out that sitting is a completely natural thing. And again, we pathologize something that's natural. Um, s- recent studies have shown, um, there's a guy named Dave Raichlen and, uh, who, who did a study of the Hadza hunter-gatherers in Tanzania, and they sit almost 10 hours a day, which is basically the same amount as, um, as Brits and, you know, Americans sit. Uh, so sitting isn't something weird and abnormal. It, but, but, but that said, um, how we sit is a little bit different.

Dr. Rangan Chatterjee 1:11:51 Yeah.

Dr Daniel Lieberman 1:11:51 So, so-

Dr. Rangan Chatterjee 1:11:51 I was gonna ask about how do they sit?

Dr Daniel Lieberman 1:11:53 So there's two important differences. The first is that many of us sit in chairs with backs. So like I have this nice back on my chair, and when I sit with that, that r- seat back, that's a very modern thing. I no longer have to use any muscles to, to kind of keep my, my back upright, and that leads to a weak back, which we think has, has related to lower back pain. The other thing is that, uh, people in non-Western societies, uh, and, and some people in Western societies g- have a lot of interrupted sitting. They just don't sit inertly for hours and hours and hours. So, uh, and it turns out that getting up every once in a while, every few minutes, every 12 minutes or 15 minutes or 10 minutes, whatever, it depends on the study, has all kinds of metabolic benefits. It's like turning on the car engine, right? It, it turns on all kinds of cellular machinery. It lowers blood sugar levels. It lowers, you know, triglyceride levels in your blood. It decreases inflammation. So you might sit the same number of hours as, as, as the next guy, but if you get, get up every once in a while, just move a little bit, that has all kinds of metabolic benefits. And then finally, maybe most importantly, it's what you do when you're not at work, right? If I sit all day at work 'cause I have a 9:00 to 5:00 job, and then I go home and then I sit in front of a TV, I'm in trouble, right? But if I sit all day at work, but I go to the gym in the morning and, you know, go for a walk and, you know, do some, do some exercise, et cetera, it's not the same thing. And it turns out that when people do epidemiological studies of sitting time against illness, it turns out that leisure time physical inactivity is far more predictive of health than work time. And so we don't often make these distinctions. So, so sitting isn't in and itself abnormal or dangerous or bad, it's how sitting fits into our overall life and how we sit, um, that is important.

Dr. Rangan Chatterjee 1:13:37 I, I, I think that, that's such a great distinction and how we sit is, is, is fascinating to me because, um, you know, sitting in these chairs, or I, I guess what we're saying is the more comfortable our chair is, in some ways the more problematic because we can have hours without actually activating muscles. We can just sort s- we can just sort of morph into the chair and not do anything. Whereas I'm guessing the hunter-gatherers don't have an alarm or a smartphone telling them to get up-

Dr Daniel Lieberman 1:14:06 [laughs]

Dr. Rangan Chatterjee 1:14:06 ... every 12 to 15 minutes, so I'm guessing they're sitting in a way that I wouldn't say is uncomfortable. Well, how do they sit? Why don't you, why don't you explain how it is that they're sitting?

Dr Daniel Lieberman 1:14:14 Well, so half the time they s- half the time they sit on the ground with their legs out, maybe 15% of the time they squat, you know, another 15% of the time they kneel, you know. But, but they're always, you know, there's children running around, there's food on the fire, there's, you know, they get up every once in a while. But they're not sitting there glued to their Zoom screen-

Dr. Rangan Chatterjee 1:14:32 Yeah

Dr Daniel Lieberman 1:14:32 ... 'cause they're, 'cause they're locked down in a pandemic, or they're not watching a, you know, a, a two-hour movie or whatever. They're, they're, they're kind of getting up all the time and, and-

Dr. Rangan Chatterjee 1:14:42 Yeah

Dr Daniel Lieberman 1:14:42 ... and we know both epidemiologically, but we also know in terms of the, the, the mechanistic biology that, you know, interrupted sitting is just way more healthy than, than uninterrupted sitting. And, and, and, and while there's nothing wrong with sitting per se, if that's all you do, then yes, you're gonna, you're, you're gonna increase your chances of, of a wide range of diseases.

Dr. Rangan Chatterjee 1:15:02 Yeah. And I'll just admit one of my own personal bugbears is [laughs] a kind of societal norm, which is to tell children to keep their bums on their seat and not move around. It's something that-

Dr Daniel Lieberman 1:15:13 Oh

Dr. Rangan Chatterjee 1:15:13 ... it, it-

Dr Daniel Lieberman 1:15:14 That's so wrong

Dr. Rangan Chatterjee 1:15:15 ... uh, uh, but of course kids wanna-

Dr Daniel Lieberman 1:15:16 Activity is good for you.

Dr. Rangan Chatterjee 1:15:17 Yeah. It's like, you know, it's like you're being a good obedient child if you sit there and don't move, which is just completely, uh, you know, it's so far removed from our innate, uh, uh, needs and wants, you know. But I watch my kids, they wanna move around. My, my son actually in his old school, he used to get told off because halfway into the lesson or 10 minutes in, he'd like, he'd want to squat on his chair. He just felt very natural and comfortable in that position. And he's like, "Bum on chair, stay still." And I'm like, and I was really conflicted 'cause I'm like, I really thought, "Well, that is, I don't want my son having to have his bum on his seat and, and stuck there for 40 minutes." Um, but it's, I think this is where your book I think is going to be incredibly helpful for society at large and just really busting a lot of these myths, having a bit more nuance in the conversation around physical activity and movements, which I think is very much needed. Uh, I, I think it's, I, I think it's such a fabulous deep dive into a topic that frankly affects all of us. I love the bit about grandparents in the book.

Dr Daniel Lieberman 1:16:20 Thank you.

Dr. Rangan Chatterjee 1:16:20 Um, and I-

Dr Daniel Lieberman 1:16:21 That's my favorite section.

Dr. Rangan Chatterjee 1:16:22 It was such a wonderful bit to read about, and I wonder if you could just sort of expand on it and why it's so important for us to remember because many people I think as they get older think that they should actually become less active, and you're sort of-

Dr Daniel Lieberman 1:16:35 No

Dr. Rangan Chatterjee 1:16:35 ... saying that may not be the case.

Dr Daniel Lieberman 1:16:37 Yeah, this is something we're, we're working on further right now. But I th- to me, I think it's maybe the most important part of the book in a way, which is that, you know, we have this idea that as you get older, you know, it's time to kick up your heels and, you know, move to Florida or whatever it is, right? And just kinda be less active and take it easy and, you know, en- enjoy the, enjoy your retirement. But, you know, humans are unusual species. We evolved, we're one of the few species that evolved to live after we reproduce. We evolved to be grandparents. But we didn't evolve just to be grandparents, you know, to enjoy our grandchildren. We evolved to be grandparents to help our grandchildren. So if you look in the hunter-gatherer societies and in farming societies, grandparents are out there foraging and hunting and gathering and digging and doing all kinds of stuff and, and helping out their children and their grandchildren, providing food surplus, you know, helping, you know, being active. And in fact, we have data showing that people tend to be, often are more active when they're grandparents than when they're parents because they don't have kids in tow, right? And, and what's important about that, it's kind of like a chicken and egg question, you know, which came first? Living long in order to be active or being active in order to live long? And, you know, they're, they're, they're both there, right? And, and it turns out that, that physical activity is really important in, in slowing processes of aging and, and decreasing disease because when you're physically active, you turn on all kinds of repair and maintenance mechanisms, right? So when you're, when you're active, you, you know, you, you stress your body, you produce reactive oxygen species. You, you know, you, you, you get, you generate heat, you do all, you turn up your, your sympathetic nervous system, your fight and flight sy- system, but then you spend energy after you're exercising to, to, to re- to deal with all that, right? We produce antioxidants. We produce molecules to fix all the proteins that we damaged because they got, you know, he- in- affected by heat. We, we, we lower our blood pre- temperature. We, we, we, we turn on our parasympathetic, you know, rest and digest system to lower sympathetic activity. We turn on all these mechanisms that keep our bodies h- repaired and, and, and maintained. And the trick is that we ne- because we never evolved not to be physically active, we never evolved to turn on these mechanisms in the absence of physical activity. We need that stress to mount the anti-stress response. And so physical activity, this is really at the heart of the book. This is why physical activity is so good for us. It, it turns on all kinds of good processes in our body that, that keep us from aging and keep us from getting sick. And so as we get older, that becomes even more important, right? You wanna keep your muscles healthy. You wanna keep your chromosomes healthy. You wanna keep your, your cells from deteriorating. You wanna keep the mitochondrial numbers up in your muscles. Uh, the, the list goes on and on and on, and that's why physical activity is so important. So as we get older, it, it becomes even more important to stay physically active because that, and, and of course the data are there. We know the epidemiological data, we know the mechanistic data, but we don't have this sort of cultural idea that, that, that, that as we age- That's the time to keep up the activity, not turn it down.

Dr. Rangan Chatterjee 1:19:36 Yeah. It's really fascinating how we've evolved to be grandparents. I really like that as an idea. Um, y- you've, you've also mentioned in the book that we've not evolved to be too strong, and I found that really interesting.

Dr Daniel Lieberman 1:19:49 Yeah. [laughs]

Dr. Rangan Chatterjee 1:19:49 Um, and it, it made me think of something, I guess I've been pondering for a while, as with this, with the sort of narrative around exercise and, you know, as a guy, you know, seeing, since I was 13 or 14, seeing Men's Health on the magazine wherever I went with a, with a ripped guy on the cover showing off his six-pack and his pecs, and being quite influenced by that, I think, as a, as a, you know, as an insecure teenager growing up. Um, you now see there's, there's some, you go into gyms and you see some, you know, really, really muscly people, um, who, who love bodybuilding. And I, I've actually had a few patients, including one when I made a BBC documentary, um, this chap who actually had body dysmorphia, and he had a real negative self-esteem issues, how he viewed himself and, you know, working out, putting on muscle was, was absolutely linked to that. And I just wanna, before you answer this, I just wanna draw a contrast. A couple of summers ago, I was in a place called Chamonix in France, which is at the foot of Mont Blanc.

Dr Daniel Lieberman 1:20:53 Yeah. Beautiful place.

Dr. Rangan Chatterjee 1:20:54 Beautiful place. Uh, I was there in the summer with my family. I've got a lot of friends there, and one day we went to the swimming pool, the outdoor swimming pool, and what was really interesting to me is that if you looked around in the pool, it, it was so noticeable to me that the physique of people in the pool, whether they were, you know, you know, above the age of 60, 70, you know, in the middle age, young, the physique of people was just a little bit different. That what you never saw, every- not everyone, but a lot of people looked really fit, but not in a, like, a really I've worked on my fitness way. So these typically would be people who live in the mountains, so they're getting around, they, they hike at the weekends, they might go cycling, uh, they might lug stuff up and down the mountains. It was almost like a functional fitness. They weren't working on being fit, yet they were actually really fit. And I, and I think in some ways that actually supports everything you're making the case for in the book. So just a few thoughts there. I wonder if you could unpack them for me.

Dr Daniel Lieberman 1:21:59 Well, yeah, I mean, it, to me, for me, the big surprise is, you know, going to a gym and realizing, I mean, I have a tiny little gym in my basement, and I've actually gone, I've bought weights whose sole function is to be lifted. [laughs] If you think about it, it's kind of a really weird thing, right? Try to explain that to your great-great-great-grandparents, that you go out and spend hard-earned money on something whose sole job is to be lifted. Like, why not just do some sit-ups or pull-ups or, you know, go out and do something in the garden, right? It's a, it's a very modern thing, right? And, and again, there's nothing wrong with it. I've done it myself. But, but, um, but we have this idea that, you know, of being ripped and buffed, and a lot of this happened, uh, I, in the book, I went into the history of this kind of modern, uh, uh, you know, physical culture. A lot of it started in the Industrial Revolution as the machines were replacing humans and, and, um, and, and people were insecure and, and, um, and I think that led to Charles Atlas and this kind of rise of this physical culture movement, this idea of being really ripped and buffed and, you know, you know, uh, Mr. Universe kind of stuff. And, and we have this idea that, you know, to be... And there's nothing wrong with being really strong. I mean, you know, there's, for, for many folks it's fun, and some people really enjoy it, but it's, it's a modern thing, right? And, and, and our ancestors not only didn't do that, but they couldn't afford to do that because muscle is a really expensive tissue. If you add a lot of muscle mass, you have to eat a lot more, too. And in a, in a world in which, which, which, uh, which where food is scarce, you can't afford to, to, um, um, to have that kind of extra muscle mass. Furthermore, you don't have nautiluses and other machines that apply, you know, constant loads no matter what the angle of your biceps are, et cetera. There is no way to kinda get that fit in, in a normal world. Uh, so, so again, uh, it's important to stay strong as you get old, uh, particularly to avoid muscle wasting, sarcopenia, which is a really serious disease of aging. Uh, you know, people have a hard time getting out of chairs and stuff like that because they lose strength. But we don't need to be super strong to be healthy. Um, and our ancestors weren't super strong. So if you wanna go to the gym and get ripped, fine, [laughs] that's perfectly okay. And, um, um, or if you enjoy, you know, looking at people whose physiques are ripped, that's fine too. But let's not pretend that this is a kind of a, a, a necessary natural thing. And I, and the other thing I think is, that I, I worry about sometimes is people, people get really into what they do, right? There are aerobic people who do cardio who hate doing weights, and people who do weights who hate doing cardio, and then they kind of self-justify what they do, right?

Dr. Rangan Chatterjee 1:24:29 Yeah.

Dr Daniel Lieberman 1:24:29 And the answer, of course, is that we, we evolve to do a mixture of, of those things. C- cardio still is the bedrock of most fitness programs, you know? As a physician, I'm sure you would know this better than most, but if you really were to do one thing to kind of work on your physical, you know, your health, cardio is probably it. But you should also add some, some weights in there, too. I mean, that's also important. And some kind of mixture is, is, is, you know, is what, is what we evolved to do, and it's probably right. And if you wanna do more of one, more of the other, that's fine, but let's not pretend that's what we evolved to do. We didn't evolve to be like super jacked, you know, cavemen, you know, Charles Atlases any more than we evolved to be, you know, Eliud Kipchoges. We, we evolved to be something in the middle.

Dr. Rangan Chatterjee 1:25:09 Yeah. And, and I, and I love your approach, um, Dan. It's very, so respectful of people's autonomy, their, their, their right to choose. It's like, "Look, you do it. Look, I'm gonna present you the science, I'm gonna present you the evolutionary story here. Yeah, if you wanna do something different, go for it. But let's not pretend it's anything other than that's your desire, that's your passion." I think that's, that's a lovely way to approach it. As we sort of close this conversation off, I do think we should briefly touch on the immune system.

Dr Daniel Lieberman 1:25:38 Oh, yeah.

Dr. Rangan Chatterjee 1:25:38 Right? Because especially in view of what's been going on in the world-

Dr Daniel Lieberman 1:25:42 Yeah

Dr. Rangan Chatterjee 1:25:42 ... a lot of people are thinking about their immune system. How does physical activity play a role in the immune system?

Dr Daniel Lieberman 1:25:50 Yeah. Well, um- Um, as I was actually doing the, the edits on the book, uh, you know, k- the lockdown had started, and I, and I r- and I, and I, I made sure that there was a, a section on respiratory tract infections. But, but the immune system is, like every system in the body, is affected by physical activity, and for the most part, just like everything else, it's, it's improved by physical activity. And, and we don't know exactly why, but I think it's because if you're, if you're in camp and doing nothing, you don't, and you don't leave, you don't encounter new pathogens, right? So I think there's a link between physical activity and immune function because as you, being physical, physically active was a, was the way in which we, we, we, you know, we left camp and, and, and got exposed to pathogens. That might be a hypothesis. Uh, and, and it's also part of this sort of repair and maintenance mechanism, but, but there's plenty of data which shows that physical activity, moderate levels of physical activity, upregulate key components of the immune system. So for, for respiratory tract infections, for example, when you're physically active, you not only produce more, uh, immune cells, like there's natural killer cells, which I love the name, right? You know

Dr. Rangan Chatterjee 1:26:57 Yeah

Dr Daniel Lieberman 1:26:58 ... they, they're, they're naturally killing things in your body. They're, they're your, they, they kill, for example, cells that become infected with viruses, right? Cytotoxic T cells, again, an important part of your immune system, upregulated by physical activity, and not only are there, you produce more of them, but there's compelling evidence that you redeploy them to vulnerable parts of your body.

Dr. Rangan Chatterjee 1:27:17 Yeah.

Dr Daniel Lieberman 1:27:17 So when you f- when you go for a run, not only do you produce more of these cells, but you send them to the, the linings of your respiratory tract, which is, guess what, where we get, we're vulnerable to COVID, right? To this, to this SARS, uh, coronavirus. In addition, uh, physical activity upregulates the humoral immune system, the antibody production. As people get older, their antibody production, uh, declines, but people who are more physically active have much healthier responses to vaccines-

Dr. Rangan Chatterjee 1:27:42 Yeah

Dr Daniel Lieberman 1:27:42 ... and produce more antibodies, and again, for the same reason. And so, uh, so by being physically inactive, we increase our vulnerability to, directly increase our vulnerability to respiratory tract infections, but physical activity also has in- indirect effects by making us more likely to be obese, to have metabolic syndrome, to have all the hypertensive, which are all the covariates that increase your risk to disease. So if we're gonna fight this, this, this, this, this, this, this pandemic, one of the key ways to keep ourselves healthy is to stay physically active. Um, that said, there's interesting evidence, and there's a big debate about whether too much activity-

Dr. Rangan Chatterjee 1:28:21 Yeah

Dr Daniel Lieberman 1:28:21 ... makes, opens a window and makes you vulnerable. And there's, to be honest, there's not a lot of data 'cause there's so few people who do too much that [laughs] we just don't have a lot of data at that end of the curve. Um, and it's still very debated. So within humans, there's not a lot of really good data, but in animal models, there certainly is. So there's, I, I cite in the book a study that is really quite extraordinary study. They, they gave mice a really virulent form of influenza, and then for the few days where the, where the mice were coping with that influenza, you know, before the symptoms emerge, while their immune system was initially, uh, dealing with it, some of the mice were, were sedentary, some of the mice, they had them exercise, like, 20 minutes a day, and some of those poor little mice, they had them exercise, like, two hours a day. And the ones who exercised moderately had less than half the, the mortality rate of the sedentary mice, but the ones who exercised ridiculous amounts had much higher mortality rates than the sedentary-

Dr. Rangan Chatterjee 1:29:15 Yeah

Dr Daniel Lieberman 1:29:15 ... mice. And to me, I think that, that highlights, I think, what every physician knows, which is that, you know, some is good, but be careful. Don't overdo it because you're gonna deplete your body of energy, and that then if there's less energy, then your, which, and your immune system takes a lot of energy, you, you, you could potentially harm yourself. So, so, so really, as we deal with the physical problems, the me- physical health, the mental health of this, this, this pandemic, but also just our, our, our, our immune health, you know.

Dr. Rangan Chatterjee 1:29:43 Yeah.

Dr Daniel Lieberman 1:29:43 Staying physically active is just absolutely crucial right now.

Dr. Rangan Chatterjee 1:29:46 Yeah. Thank you. That's a, it was a really nice summary of, of the research there a- and sort of how it helps. Daniel, look, thank you so much for your time today. Thanks for writing such a wonderful book. Um, I always like to finish off conversations with some practical tips for people. So the c- the, the podcast is called Feel Better, Live More. When we feel better in ourselves, we're gonna get more out of life, and I'm sure, you know, when we move more, when we move in a way that makes us feel good, that, that allows us to move regularly, we're gonna probably live longer, and we're gonna feel better in ourselves. So do you have a few sort of practical tips for people so they can think about and th- start applying them into their lives immediately to start improving their health and wellbeing?

Dr Daniel Lieberman 1:30:36 Well, I think, um, I think the tip would vary depending upon the kind of person. So if you're somebody who's struggling to get enough exercise, right, if you don't get enough and you'd like to exercise more, um, I think that, you know, there's lots of things you can do, but I think the most important thing is to find somebody who f- who, like, who, who you wanna exercise with. Get, get an exercise buddy, um, and, and, and use each other to help each other. Um, there's nothing like, you know, having a, you know, somebody who you meet for a walk or a run or whatever, and don't feel like you have to, you know, you have to go crazy, you know? S- s- some is better than none, and, and, and once you get better, you enjoy some, then you might decide that you wanna do a little bit more, but don't feel like there's an optimal kind of exercise or you, you know, whatever, just, you know, that you have to do it. Don't make it, you know, don't make it un-fun. Make it fun, and, and if you d- make it fun and make it part of your life, and recognize also that your body has to adapt. It takes time. One of the problems, for example, of being obese is that, um, is that you have less dopamine response to exercise, and dopamine is the molecule that makes you wanna do more. It's the reward molecule, and obesity actually down regulates that. And so we have these expectations that all of a sudden you exercise and a, and a week later you're gonna feel great. Well, it's gonna take more than a week, and, and you have to be in it for the long term, not the short term. And, and so don't do it just for the For the health benefits, do it be- for the social benefits. Do it for all the other things. And if you make it fun and part of your life, um, um, and find ways to make it necessary, um, I think that's the most important thing that we... You know, that's the most important tip, and there are so many ways to do that. I, I, for example, leave my exercise clothes out in the morning when I go to bed so that when I wake up, that's what I put on, and that, like, helps. It's like it removes one less barrier to, to starting my run, 'cause I never wanna go for a run in the morning when I start. Never, ever, on no occasion whatsoever, um, do I ever do that

Dr. Rangan Chatterjee 1:32:26 And, and, a- a- and how many marathons have you done now?

Dr Daniel Lieberman 1:32:29 I just did my 25th.

Dr. Rangan Chatterjee 1:32:31 Well, first of all, congratulations. But that, I think, is, is so valuable there at the end, what you said, Daniel, that you've had to find ways to remove barriers to that because you don't want to.

Dr Daniel Lieberman 1:32:45 Yeah.

Dr. Rangan Chatterjee 1:32:45 Yeah. You've just completed your 25th marathon. You don't want to get up and go for a run, yet you are a runner. And-

Dr Daniel Lieberman 1:32:52 Right. And, and, and I-

Dr. Rangan Chatterjee 1:32:53 ... that's really, that's really, really key, isn't it?

Dr Daniel Lieberman 1:32:56 I, I, I, I ne- there's never been a time when I left the door of my house thinking, "I really wanna run." I'm always like, "Eh, I'm gonna force myself to run." And then I always enjoy it when I come back. Um, another example is the, in my, my building, right? Um, I live in, I, my, my, my, my office, when I get to go to it again aft- after the lockdown, my office is on the fifth floor of this beautiful old Victorian building, and every day when I walk into the building, I wanna take the elevator, bar none. I always look at the elevator longingly. But the reason I don't take the elevator is that if anybody sees, um, me taking the elevator, they'll call me a hypocrite. And, and, and it's, so it's not because I, I'm doing it for my health. I'm doing it because [laughs] because I, I have a social, I have a s- I have, I've socially coerced myself into, into taking the stairs, and I never regret having taken the stairs by the time I get to the fifth floor. But I always regret taking the stairs as I head up the stairs looking longingly at the elevator. And don't beat yourself up for, for, for, for those instincts. Those instincts, even though elevators never existed in the Stone Age, it is a completely normal, natural instinct to wanna avoid exertion, and don't ever feel bad about it.

Dr. Rangan Chatterjee 1:34:05 Yeah. Wonderful closing thoughts there. Uh, you have found a way to make it work for you. Certainly that's what all of us individually have to do. We've gotta find a way that, that, that works for us, that we can be more physically active. Daniel, thank you for your time today.

Dr Daniel Lieberman 1:34:19 My pleasure.

Dr. Rangan Chatterjee 1:34:20 Thanks for such a wonderful book and, um, I look forward to the next time we get to have a conversation.

Dr Daniel Lieberman 1:34:26 Thanks. Great interview. I really appreciate it.

Dr. Rangan Chatterjee 1:34:28 [upbeat music] Press subscribe to get more inspiration and ideas on how to feel better so you can get more out of life. And if you have a moment, why not check out this conversation that I've picked out as a perfect follow-up? Remember, lifestyle change is always worth it, because when you feel better, you live more.