Why Runners Get Stomach Problems (And How to Fix It): Dr Marc Bubbs

Brady Holmer sits down with Dr. Marc Bubbs — performance nutritionist, author, and creator of ProBio Nutrition — to break down everything runners need to know about gut health. From identifying food triggers to fueling on race day without GI disaster, Dr. Bubbs shares 20+ years of experience working with Olympians, pro athletes, and everyday runners. Whether you're dealing with chronic bloating or trying to push your carb intake past 60g/hour, this episode has you covered.

Brought to you by ProBio Nutrition - your all-in-one daily supplement for runners.  Get 40% off with code RLRH (or 50% off + free shipping with a subscription) ➡️

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📚 Dr. Bubbs' books: Peak and Peak 40 

🌐 drbubbs.com | probionutrition.com 

📱 Follow Dr. Bubbs on Instagram & YouTube: @drbubbs

0:00 Introduction & Dr. Mark Bubbs' Background 

1:07 Crossover Between Elite Athletes & General Population 

2:04 Gut Health as a Buzzword — What Does It Actually Mean? 

2:47 The 4 Pillars of Good Gut Health (King's College Framework) 

5:47 Three Gut Health Scenarios: Poor → Good → Great 

6:19 Scenario 1: Red & Yellow Flags — When to See a Doctor 

9:14 The Difficulty of Identifying Problem Foods 

9:54 Exercise-Related vs. Everyday GI Symptoms 

11:42 Why You Should Start With Breakfast 

12:07 The 3-4 Hour Detective Method 

13:59 Can GI Symptoms Actually Be Resolved? 

15:02 Eating Out vs. Cooking at Home

16:09 Are Food Sensitivity Tests Worth Your Money? 

18:37 Scenario 2: When Running Triggers GI Distress 

19:48 How Getting Fitter Improves Gut Diversity 

20:57 GI Symptom Rates: Ultras, Ironman, Team Sports & Running 

22:50 Finding Your Carb Intake Inflection Point 

24:17 Gut Training: Titrating Up From 60g/hr 

25:36 Is Pushing Above 80g/hr Worth the Risk? 

26:00 Fueling Advice for Slower Marathon Runners 

26:56 — AD BREAK — 

28:08 Best Ways to Train Your Gut 

29:06 Race Day Anxiety & the Gut-Brain Connection 

31:20 Building Gut Health Over Months of Training 

31:41 The 30 Food Diversity Challenge 

33:08 Does Getting Fitter Reduce GI Symptoms? (The Bell Curve) 

35:12 Probiotics for Colds, Travel & Performance 

36:30 Race Week & Race Morning: What to Do and Avoid 

38:47 Pro Tip: Caffeinated Gum Before the Start Line 

39:06 The Golden Rule — Don't Try Anything New on Race Day 

39:30 Carb Mouth Rinsing: The Placebo That Works 

40:00 Scenario 3: Optimizing Gut Health for Performance 

41:08 Prebiotics Explained — Seeds for Your Gut Garden 

43:47 Best Whole Foods for Gut Health (By Category) 

46:28 The Truth About Processed Food & Your Gut 

47:47 Knowledge vs. Execution: The Real Friction Point 

49:00 ProBio ProBlend: Why Dr. Bubbs Created It 

53:00 Where to Find Dr. Bubbs, His Books & ProBio