How the microbiome affects metabolism and body weight | Dr Will Bulsiewicz, MD

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Dr Will Bulsiewicz is an absolute powerhouse when it comes to the science of gut health and the microbiome. He’s also a favourite on The Proof, dating back to his ground-breaking first appearance on Episode #17 of the show.

Having returned to The Proof multiple times since that initial episode, Dr Bulsiewicz has joined me to explore various topics, including building the foundations of a healthy gutwhy people quit plant-based diets, and most recently, how to heal your microbiome after antibiotics. In Episode #275, we shift our focus to how the microbiome affects metabolism.

“People who consume more dietary fibre are less likely to have a heart attack, are less likely to die of heart disease, are less likely to have a stroke, are less likely to be diagnosed with diabetes, are less likely to die of any cardiovascular disease – whether it be a heart attack or a stroke – and are less likely to die, period.”

Known as “Dr B”, Dr Will Bulsiewicz is a renowned gastroenterologist and a leading authority on gut health on the international stage. He is the author of the New York Times bestsellers Fiber Fueled and The Fiber Fueled Cookbook and has been honoured with awards in his field. In addition to serving as the US Medical Director and being a member of the Scientific Advisory Board for ZOE, a personalised nutrition company, Dr Bulsiewicz has contributed to over twenty peer-reviewed scientific journals. He has presented more than forty times at national meetings, presented to Congress and the USDA, and helped educate and guide more than 10,000 students on their journey to achieve optimal gut health.

“Your microbiome predicts your blood sugar more so than your waist circumference does.”

In today’s conversation, we zoom in on the three ways that the microbiome affects our metabolism: through energy balance, blood glucose control (insulin resistance), and blood lipids.

You’ll learn about why eating more fibre is the key to controlling body weight and reducing your risk of disease. We also compare ketogenic and plant-based diets through a scientific lens, discuss how evolution can make our body work against us, and assess GLP-1 agonists such as Ozempic.

Specifically, we cover:

  • Intro (00:00)
  • Introduction to Dr. Will Bulsiewicz and His Literary Contributions (2:42)
  • Do Gastroenterologists Analyse Their Own Stool? (7:43)
  • Dr. Will Bulsiewicz’s Collaboration with ZOE (9:55)
  • Behind the Scenes: Dr. Will’s Nutritional Supplement Venture (11:20)
  • The Progressive Journey of the Gut Health Movement (14:02)
  • Decoding the Microbiome: Its Role and Significance in Health (17:20)
  • Exploring Metabolism and Metabolic Health (0:24:50)
  • The Microbiome’s Role in Influencing Metabolism (0:33:07)
  • Understanding GLP-1 Agonists: Their Impact on Satiety and Weight Reduction (0:38:54)
  • Tips to Increase Dietary Fibre Intake for Better Health (0:45:05)
  • The Connection Between Microbiome and Fat Metabolism (0:47:36)
  • Strategies to Boost Metabolism and Promote Brown Fat Activation (0:49:59)
  • The Role of Lipopolysaccharide in Gut Barrier Functionality (0:51:33)
  • Significance of Gut Health and the Risks of Dysbiosis (0:54:49)
  • Linking Insulin Resistance with Satiety Mechanisms (0:56:03)
  • The Relationship Between Satiety and Blood Sugar Fluctuations (0:58:30)
  • Analysing Kevin Hall’s Research: Plant-Based Diet vs. Alternative Diets (1:02:04)
  • Blood Regulation, Insulin Resistance, Lipotoxicity, and Microbiome (1:10:38)
  • Deciphering Glucose Homeostasis: What You Need to Know (1:20:37)
  • The Interplay Between Insulin Resistance and Obesity Factors (1:21:51)
  • The Beneficial Role of Dietary Fibre in Blood Sugar Management (1:23:11)
  • Is Reversing Type 2 Diabetes a Possibility? (1:25:18)
  • How the Microbiome Influences Blood Sugar Regulation Mechanisms (1:32:12)
  • The Cholesterol-Lowering Benefits of Dietary Fibre (1:37:06)
  • Top Sources of Soluble Fibre for a Healthy Diet (1:39:40)
  • Triglycerides and Their Relationship with the Microbiome (1:42:06)
  • The Protective Role of Fibre in Disease Prevention (1:46:28)
  • Outro (1:51:46)

Episodes featuring Dr Bulsiewicz are always incredibly valuable, and this one is no different. I hope this conversation helps you understand how the microbiome interacts with metabolism, and that you gained other key insights into body weight and gut health.

Connect with Dr Will Bulsiewicz on InstagramFacebookTwitter, and TikTok. Discover more resources and Dr B’s books on his website,, learn more about supplementation at, and find his work on personalised nutrition at Listen to Dr B’s past appearances on The Proof here.

My team and I have also put together a PDF of resources for this episode, helping you better understand the science behind this conversation. Download it at

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Enjoy, friends.


More about Dr Will Bulsiewicz

Dr Will Bulsiewicz (or “Dr B”) is an award winning gastroenterologist, internationally recognized gut health expert and the New York Times-bestselling author of Fiber Fueled and The Fiber Fueled Cookbook. He is the US Medical Director and on the Scientific Advisory Board of personalized nutrition company ZOE, has authored more than twenty articles published in peer-reviewed scientific journals, has given more than forty presentations at national meetings, presented to Congress and the USDA, and has taught over 10,000 students how to heal and optimize their gut health. He lives in Charleston, South Carolina with his wife and children.

Supporting studies

Head over to the Reference Page.

  • A Plant-Based Meal Increases Gastrointestinal Hormones and Satiety More Than an Energy- and Macronutrient-Matched Processed-Meat Meal in T2D, Obese, and Healthy Men: A Three-Group Randomized Crossover Study • PMID: 30642053
  • Carbohydrate quality and human health: a series of systematic reviews and meta-analyses • PMID: 30638909
  • Effect of a plant-based, low-fat diet versus an animal-based, ketogenic diet on ad libitum energy intake • PMID: 33479499
  • Gut bacteria selectively promoted by dietary fibers alleviate type 2 diabetes • PMID: 29590046
  • Human postprandial responses to food and potential for precision nutrition • PMID: 32528151

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