The No.1 Poo & Gut Scientist: If Your Poo Looks Like This Go To A Doctor! Dr Will Bulsiewicz
Steven Bartlett (host), Dr Will Bulsiewicz (guest), Narrator
In this episode of The Diary of a CEO, featuring Steven Bartlett and Dr Will Bulsiewicz, The No.1 Poo & Gut Scientist: If Your Poo Looks Like This Go To A Doctor! Dr Will Bulsiewicz explores transform Your Gut, Transform Your Life: Poop, Microbes, and Metabolism Dr. Will Bulsiewicz, a gastroenterologist and gut microbiome researcher, explains how gut health underpins digestion, immunity, metabolism, mood, hormones, and even sexual function. He argues that most modern chronic conditions—from IBS and obesity to depression and autoimmune disease—are tightly linked to a damaged gut microbiome and a weakened gut barrier.
Transform Your Gut, Transform Your Life: Poop, Microbes, and Metabolism
Dr. Will Bulsiewicz, a gastroenterologist and gut microbiome researcher, explains how gut health underpins digestion, immunity, metabolism, mood, hormones, and even sexual function. He argues that most modern chronic conditions—from IBS and obesity to depression and autoimmune disease—are tightly linked to a damaged gut microbiome and a weakened gut barrier.
Throughout the conversation he demystifies microbes, the gut–brain connection, short-chain fatty acids, and why poop is a crucial diagnostic signal rather than something to ignore. He outlines how diet quality—especially fiber-rich, plant-diverse, and fermented foods—rapidly reshapes the microbiome and can outperform drugs for prevention and often for reversal of metabolic disease.
The episode also covers alcohol’s impact on gut health, the limitations and risks of weight-loss drugs like Ozempic, the promise and complexity of fecal transplants, and how relationships, stress, trauma, and even sexual attraction relate back to microbes. It closes with practical, sustainable steps (Dr. B’s “F-GOALS”) to build a resilient microbiome for yourself and future generations.
Key Takeaways
Your gut microbiome is central to nearly every system in your body.
We host around 38 trillion microbes, mostly bacteria, concentrated in the colon. ...
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Food is the dominant “medicine” shaping your microbiome—far more than pills.
Across a lifetime, we consume ~36,300 kg of food versus milligrams of pharmaceuticals. ...
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Poop is a free, powerful window into gut health—don’t ignore it.
About 60% of stool weight is microbial in origin. ...
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Fiber and plant diversity are the most leveraged tools you have.
Most Westerners eat only 10–15 different plants per week; research (American/British Gut Projects) links better microbiome diversity to ~30+ plants weekly (fruits, vegetables, whole grains, legumes, nuts, seeds, herbs, spices). ...
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You can’t shortcut a bad lifestyle with drugs or alcohol without paying a price.
Weight-loss drugs like semaglutide (Ozempic/Wegovy) mimic the satiety hormone GLP‑1, but have digestive side effects, unknown long-term risks, and often require indefinite use—stopping tends to bring weight back. ...
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Fecal transplants and microbial “extinction” point to a future of super-probiotics—and serious ethical questions.
Fecal microbiota transplantation (FMT) already cures otherwise intractable C. ...
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Relationships, stress, trauma, and sex are deeply microbiome-linked, not just ‘psychological.’
Co-habiting people share microbes; couples with stronger emotional connection share more and have healthier microbiomes than those living together but disconnected. ...
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Notable Quotes
“If your poop looks like this, to me that's grounds to talk to a doctor.”
— Dr. Will Bulsiewicz
“On your thumb, there are as many microbes as there are people in the UK.”
— Dr. Will Bulsiewicz
“The choices that you make today, within 24 hours, will have an effect on your microbiome.”
— Dr. Will Bulsiewicz
“I want people to eat a diet where they can eat as much as they want without restriction and still achieve their weight goals.”
— Dr. Will Bulsiewicz
“We have stigmatized poop. We're not allowed to look in the bowl. We should be looking in the bowl.”
— Dr. Will Bulsiewicz
Questions Answered in This Episode
You mentioned that SCFAs can flip genes on and off and modulate autoimmunity; what specific human studies would you point to that most convincingly show diet-driven SCFA changes reversing or stabilizing autoimmune diseases?
Dr. ...
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In practice, how do you differentiate between a ‘normal’ Bristol 5 from a very high-fiber diet and a Bristol 5 that indicates underlying malabsorption or inflammation requiring medical workup?
Throughout the conversation he demystifies microbes, the gut–brain connection, short-chain fatty acids, and why poop is a crucial diagnostic signal rather than something to ignore. ...
Get the full analysis with uListen AI
Given the striking obesity and mood-transfer results from human-to-mouse fecal transplants, what do you see as the main biological and regulatory barriers to safely using targeted FMT in humans for obesity or depression?
The episode also covers alcohol’s impact on gut health, the limitations and risks of weight-loss drugs like Ozempic, the promise and complexity of fecal transplants, and how relationships, stress, trauma, and even sexual attraction relate back to microbes. ...
Get the full analysis with uListen AI
Your data link alcohol intake to real-time increases in circulating LPS; what, if any, threshold of drinking (e.g., one small glass of wine) appears safe for the gut barrier, or is the truly gut-safe recommendation complete abstinence?
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The generational loss-of-diversity studies in mice are alarming; if a young adult today wants to ‘reset’ as much as possible for their future children, what concrete multi-year plan—diet, environment, antibiotic stewardship—would you recommend to maximize the microbiome they pass on?
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Transcript Preview
What I have here is a variety of different shapes and sizes of poop.
Yeah.
What does this tell us about our health?
Well, if your poop looks like this, to me that's grounds to talk to a doctor.
Dr. Will Bulsiewicz.
World-renowned gut health doctor... Who has a wealth of information on...
How we can improve our gut health through food and lifestyle changes.
We are currently living through an epidemic of gut health issues, and if we want to be healthy humans, we absolutely need a healthy gut microbiome in order to accomplish that. So let's break this down. First of all, microbes are invisible. On your thumb, there are as many microbes as there are people in the UK.
Really?
And gut microbes play a critical and essential role in controlling whether or not you suffer from depression because 95% of the happy hormone is produced by the gut. It controls your cognition, your memory, your energy levels. Your gut is the place where you are making decisions, and study after study after study shows us that when people eat more ******, not only do they empower the gut microbes, but also they lose weight, they're less likely to die of heart disease, less likely to be diagnosed with multiple different types of cancer.
No way.
Yes.
What about alcohol?
The science is clear. When we drink to the point of having a hangover, is that dehydration? Absolutely not. The issue is you have caused significant damage to your microbiome. But the gut is forgiving, and the choices that you make today, within 24 hours, will have an effect on your microbiome. I want people to eat a diet where they can eat as much as they want without restriction and still achieve their weight goals. And this is completely possible by consuming a diet that's...
Quick one. This is really, really fascinating to me. On the back end of our YouTube channel, it says that 69.9% of you that watch this channel frequently over the lifetime of this channel haven't yet hit the subscribe button. I just wanted to ask you a favor. It helps this channel so much if you choose to su- subscribe. Helps us scale the guests, helps us scale the production, and it makes the show bigger. So if I could ask you for one favor, if you've watched the show before and you've enjoyed it and you like this episode that you're currently watching, could you please hit the subscribe button? Thank you so so much, and I will repay that gesture by making sure that everything we do here gets better and better and better and better. That is a promise I'm willing to make you. Do we have a deal? Dr. Will, if someone just clicked on this conversation and they've- they're deciding whether to listen or not, what would be the pitch to those people? What's the benefit if they stick around?
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