Gut Health Expert: The Science of Fiber, Microbiome & Longevity | Dr. Karan Rajan

Your gut is running more of your life than you think.I sit down with Dr. Karan Rajan, NHS surgeon, gut health researcher, and one of the clearest science communicators working today, to talk about why fiber is one of the most powerful levers you have for long-term health, how the gut shapes your mood and brain function, and what most people are getting dangerously wrong about protein, GLP-1s, and extreme elimination diets.This isn't a conversation about cleanses or cutting food groups. It's about understanding your gut as a living system that responds directly to what you feed it, within 48 hours.What we explore:- How the gut microbiome directly shapes mood, mental health, and brain function and why diet is often the missing variable in depression treatment.- Why high-protein, low-fiber eating is silently damaging your colon and what the data says about finding the right balance.- What prebiotics, probiotics, and polyphenols actually do inside your body and how to combine them for maximum impact without buying a single supplement.- How GLP-1 medications affect the gut microbiome and why you have to plan proactively for fiber and nutrient deficiencies if you're on one.- Why fasting, spices, and something as simple as eating with your hands can meaningfully shift your gut health and the four lifestyle levers that matter more than any test or supplement.Chapters:00:00 Introduction02:24 Why High Performers Are the Last to Take Care of Themselves07:07 From Gut Surgeon to Microbiome Advocate: Dr. Karan Rajan's Origin Story10:09 The Gut Bacteria Linked to Depression That Antidepressants Ignore14:00 Prebiotics vs Probiotics vs Polyphenols: What Each One Actually Does17:31 How to Add Fiber Without Destroying Your Social Life20:36 The Protein Mistake Even Healthy People Make29:21 How to Optimize the Pregnant Microbiome Before and During Pregnancy33:12 What Your Poop Tells You That Your Oura Ring Never Will43:36 Fasting Windows, Saunas, and What Science Says About Gut Health47:23 GLP-1s Are Changing Your Microbiome: What You Need to Add Back57:06 Why Treating One Organ at a Time Is Failing Patients01:07:27 10 More Grams of Fiber Cuts Colon Cancer Risk by 10%About Dr. Karan Rajan:Dr. Karan Rajan is an NHS surgeon and clinical lecturer who trained in general and colorectal surgery before becoming one of the most trusted voices in online health education. His content, reaching millions across social media, strips medical science down to what's actionable, without losing the rigor. He's the author of This Book May Save Your Life and This Is Vital Information, and the co-founder of Loam, a fiber supplement built on the science he spent years researching. He lives at the intersection of clinical credibility and genuine accessibility, which is a rare and useful place to be.Connect with Dr. Karan Rajan:Instagram: https://www.instagram.com/drkaranrajan/TikTok: https://www.tiktok.com/@dr.karanr–This episode is sponsored by:RITUAL: So sit back and raise a glass to your new evening Ritual with Magnesium+. Save 25% on your first month at Ritual.com/GABBY. TIMELINESupport your cells and how you age with Mitopure® Gummies from Timeline. Visit https://timeline.com/GABBY to up to 39% off your Mitopure® Gummies. ANNMARIE: Visit https://www.annmariegianni.com/ and use code Gabby for 20% off.TRUE NUTRITION:Get 20% off your first custom blend at truenutrition.com/GABBY with code GABBY–The Gabby Reece ShowThis is where I have real conversations with the people I find most worth listening to: scientists, athletes, coaches, parents, and thinkers who are doing the hard work of building a life that holds up over time. No hacks. No quick fixes. Just honest, practical conversations about performance, longevity, relationships, and what it actually takes to show up well at every age.If you are here, you probably already know that health is not a destination. It is how you live. I am glad you are along for it.Connect with Gabby