The Science of Hunger & Medications to Combat Obesity | Dr. Zachary Knight

(uptempo music) Welcome to the Huberman Lab Podcast, where we discuss science and science-based tools for everyday life. I'm Andrew Huberman, and I'm a professor of neurobiology and ophthalmology at Stanford School of Medicine. My guest today is Dr. Zachary Knight. Dr. Zachary Knight is a professor of physiology at the University of California San Francisco and an investigator with the Howard Hughes Medical Institute. For those of you that don't know, Howard Hughes Medical Investigators are selected from an extremely competitive pool of applicants and have to renew in order to maintain their investigatorship with the Howard Hughes Medical Institute every five years or so, placing him in the most elite of categories with respect to research scientists. His laboratory focuses on homeostasis, in particular, what drives our sense of hunger, what drives our sense of thirst, and what controls thermoregulation, which is the ability to maintain body temperature within a specific safe range. Today, we mainly focus on hunger. Dr. Zachary Knight explains the biological mechanisms for craving food, for consuming food, and believe it or not, you have brain circuits that actually determine how much you're likely to eat even before you take your very first bite. And he explains the biological mechanisms for satiety. That is, the sense that one has had enough of a particular food or food group. Dr. Knight also explains the role of dopamine in food craving and consumption, which I think everybody will find very surprising, because it runs countercurrent to most people's understanding of what dopamine does in the context of eating and other cravings. Today's discussion also includes a deep dive into GLP-1, glucagon-like peptide, and the novel class of drugs such as Ozempic and Mounjaro and other related compounds that are now widespread in use for the reduction in body weight. Dr. Knight explains how GLP-1 was first discovered and how these drugs were developed, how they work, and importantly, why they work, and how that is leading to the next generation of so-called diet drugs or drugs to treat obesity, diabetes, and related syndromes. We also discuss thirst and the intimate relationship between water consumption and food consumption, and we also talk about the relationship between sodium intake, water intake, and food intake. By the end of today's conversation, you will have learned a tremendous amount about the modern understanding of hunger, thirst, and salt intake, as well as this modern class of drugs such as Ozempic and related compounds, all from a truly world-class investigator in the subjects of researching hunger, thirst, and thermal regulation. Before we begin, I'd like to emphasize that this podcast is separate from my teaching and research roles at Stanford. It is, however, part of my desire and effort to bring zero cost to consumer information about science and science-related tools to the general public. In keeping with that theme, I'd like to thank the sponsors of today's podcast. Our first sponsor is BetterHelp. BetterHelp offers professional therapy with a licensed therapist carried out entirely online. Now, I've been doing weekly therapy for well over 30 years. Initially, I didn't have a choice. It was a condition of being allowed to stay in high school. But quickly, I realized that therapy is an extremely important component to our overall health. In fact, I consider doing regular therapy as important as getting regular cardiovascular exercise and resistance training, which of course I also do every week. Now, there are essentially three things that great therapy provides. First of all, it requires that you have a really good rapport with the therapist, somebody that you can trust and talk to about what's really going on in your life. And of course, an excellent therapist will provide you support in moving towards the things that are going to grow your life in the best ways. And third, and this is the one that people often overlook, an expert therapist is somebody who can really provide you useful insights that would not otherwise be obvious to you. With BetterHelp, they make it very easy to find the therapist with whom you can have those three essential and highly effective components. If you'd like to try BetterHelp, you can go to betterhelp.com/huberman to get 10% off your first month. Again, that's betterhelp.com/huberman. Today's episode is also brought to us by Eight Sleep. Eight Sleep makes smart mattress covers with cooling, heating, and sleep tracking capacity. Now, I've spoken many times before on this podcast about the critical need for us to get adequate amounts of quality sleep each night. One of the best ways to ensure a great night's sleep is to control the temperature of your sleeping environment, and that's because in order to fall and stay deeply asleep, your body temperature actually has to drop by about one to three degrees. And in order to wake up feeling refreshed and energized, your body temperature actually has to increase by about one to three degrees. Eight Sleep makes it incredibly easy to control the temperature of your sleeping environment by allowing you to program the temperature of your mattress cover at the beginning, middle, and end of the night. I've been sleeping on an Eight Sleep mattress cover for well over three years now, and it has completely transformed my sleep for the better. Eight Sleep recently launched their newest generation pod cover, the Pod 4 Ultra. The Pod 4 Ultra has improved cooling and heating capacity, higher fidelity sleep tracking technology, and it also has snoring detection that, remarkably, will automatically lift your head a few degrees to improve your airflow and stop your snoring. If you'd like to try an Eight Sleep mattress cover, you can go to eightsleep.com/huberman to save $350 off their Pod 4 Ultra. Eight Sleep currently ships to the USA, Canada, UK, select countries in the EU, and Australia. Again, that's eightsleep.com/huberman. Today's episode is also brought to us by Waking Up. Waking Up is a meditation app that offers hundreds of guided meditation programs, mindfulness trainings, yoga nidra sessions, and more.I started practicing meditation when I was about 15 years old, and it made a profound impact on my life. And by now, there are thousands of quality peer-reviewed studies that emphasize how useful mindfulness meditation can be for improving our focus, managing stress and anxiety, improving our mood, and much more. In recent years, I started using the Waking Up app for my meditations because I find it to be a terrific resource for allowing me to really be consistent with my meditation practice. Many people start a meditation practice and experience some benefits, but many people also have challenges keeping up with that practice. What I and so many other people love about the Waking Up app is that it has a lot of different meditations to choose from, and those meditations are of different durations. So it makes it very easy to keep up with your meditation practice, both from the perspective of novelty, you never get tired of those meditations. There's always something new to explore and to learn about yourself and about the effectiveness of meditation. And you can always fit meditation into your schedule, even if you only have two or three minutes per day in which to meditate. I also really like doing yoga nidra, or what is sometimes called non-sleep deep rest, for about 10 or 20 minutes, because it is a great way to restore mental and physical vigor without the tiredness that some people experience when they wake up from a conventional nap. If you'd like to try the Waking Up app, please go to wakingup.com/huberman where you can access a free 30-day trial. Again, that's wakingup.com/huberman to access a free 30-day trial. And now for my discussion with Dr. Zachary Knight. Dr. Zachary Knight, welcome.