Learning from Dr. Will Bulsiewicz
The gastroenterologist who proved your gut is the control center for everything
The Story
Will Bulsiewicz was a success by every conventional measure: elite medical training at Georgetown, Northwestern, and UNC. Chief Medical Resident. Chief Gastroenterology Fellow. Published researcher. The career trajectory of a future department head.
But at age 33, he was 50 pounds overweight, with high blood pressure, high cholesterol, and constant anxiety. A gut health expert who couldn't heal his own gut.
Then he changed one thing: he started eating plants—lots of different plants. Within months, he lost the weight, normalized his blood pressure, and eliminated his anxiety. Without medications. Without surgery.
This "n=1" experiment sent him back to the research with fresh eyes. What he found became Fiber Fueled: the most compelling argument that your gut microbiome isn't just about digestion—it's the master regulator of your entire body.
Who is Dr. Will Bulsiewicz?
| Credential | Detail |
|---|---|
| Role | U.S. Medical Director at ZOE, Adjunct Professor at Emory University |
| Known For | "Fiber Fueled" protocol, 30 plants per week rule, F-GOALS framework |
| Books | Fiber Fueled, The Fiber Fueled Cookbook (New York Times bestsellers) |
| Background | Georgetown MD, Northwestern Chief Resident, UNC Chief GI Fellow, NIH-funded epidemiology researcher |
What makes Bulsiewicz unique: he has both clinical gastroenterology expertise AND formal epidemiology training, letting him bridge patient care with population-level research.
What ISP Students Learn
Lesson 1: The 30 Plants Per Week Rule
The American Gut Project—the largest open-source microbiome study ever—found one clear pattern:
People who ate 30+ different plants per week had the healthiest, most diverse microbiomes.
Not vegan vs. meat-eater. Not keto vs. low-fat. Plant diversity was the single best predictor of gut health.
Why diversity matters:
- Different plants contain different fibers
- Different fibers feed different bacterial species
- More species = more resilient ecosystem
- More resilient ecosystem = better health
What counts as a "plant":
- Vegetables, fruits, legumes, whole grains, nuts, seeds
- Herbs and spices count!
- Different colors of the same vegetable count separately
What this means for athletes: Don't eat the same "healthy" foods every day. Variety feeds your gut bacteria, and your gut bacteria control inflammation, recovery, and even mood.
Lesson 2: The F-GOALS Framework
To hit 30 plants, Bulsiewicz created a simple checklist:
| Letter | Category | Examples |
|---|---|---|
| F | Fruit & Fermented | Berries, apples, yogurt, sauerkraut, kimchi |
| G | Greens & Grains | Kale, spinach, oats, quinoa, brown rice |
| O | Omega-3s | Walnuts, flaxseed, chia seeds, hemp seeds |
| A | Aromatics | Garlic, onions, leeks, ginger, turmeric |
| L | Legumes | Beans, lentils, chickpeas, peas |
| S | Sulforaphane | Broccoli, cauliflower, Brussels sprouts, cabbage |
The insight: If you hit all six categories daily, you're automatically eating diverse plants.
What this means for athletes: Use F-GOALS as a daily checklist. If you're missing a category, add something from it.
Lesson 3: Short-Chain Fatty Acids (SCFAs)—The Gut's Secret Weapon
When gut bacteria ferment fiber, they produce short-chain fatty acids (SCFAs)—especially butyrate, acetate, and propionate. These compounds do remarkable things:
| SCFA Effect | Why It Matters for Athletes |
|---|---|
| Fuel gut lining cells | 70% of colonocyte energy comes from butyrate |
| Strengthen gut barrier | Prevents "leaky gut" and systemic inflammation |
| Regulate immune system | 70% of your immune system is in your gut |
| Control appetite | Influence satiety hormones GLP-1 and PYY |
| Affect brain chemistry | Gut-brain axis impacts mood and focus |
The key insight: Without fiber, your gut bacteria can't make SCFAs. Without SCFAs, your gut barrier weakens, inflammation increases, and everything downstream suffers.
What this means for athletes: Fiber isn't just about regularity. It's about producing the compounds that control inflammation, immune function, and recovery.
Lesson 4: The Fiber Paradox
Here's the irony Bulsiewicz sees constantly: the people who need fiber most are often the ones who tolerate it least.
The cycle:
- Low-fiber diet → gut bacteria population shrinks
- Smaller population → less ability to digest fiber
- Eating fiber → bloating, gas, discomfort
- Person avoids fiber → bacteria shrink further
The GROWTH strategy for building tolerance:
- Gradually increase fiber (add 5g per week, not 30g overnight)
- Record symptoms (identify specific triggers)
- Overhaul with diversity (don't rely on one fiber source)
- Water (fiber needs water to work)
- Time (gut adaptation takes 2-4 weeks)
- Heat (cooking breaks down fiber, making it gentler)
What this means for athletes: If fiber makes you uncomfortable, that's a sign you need MORE fiber, not less—just introduced gradually.
Key Takeaways
| Lesson | One-Liner |
|---|---|
| 30 plants/week | Diversity beats any specific diet label |
| F-GOALS daily | Hit all six categories to ensure variety |
| SCFAs are the payoff | Fiber → fermentation → compounds that heal |
| Build tolerance gradually | If fiber causes problems, add it slowly—don't avoid it |
How This Shows Up at ISP
Dr. B's gut-centric approach informs the Bio Skill Tree in MyPath:
- Gut Health tracks plant diversity (the "30 Plants Tracker")
- The "F-GOALS Week" challenge introduces all six categories
- Fueling Consistency emphasizes fiber-rich whole foods
- Recovery Protocol connects gut health to inflammation and healing
When ISP students understand their gut microbiome, they have a lever that affects almost everything—energy, recovery, mood, and immune function.
The Controversy
Bulsiewicz is a strong advocate for plant-based eating, which puts him at odds with carnivore and keto communities. Common criticisms:
- Some argue fiber isn't necessary for gut health (carnivore perspective)
- His supplement company (38TERA) creates potential conflicts of interest
- Individual responses to fiber vary widely
ISP's approach: We teach the core principle—gut diversity matters— while acknowledging that individual needs vary. The "30 plants" target is aspirational, not mandatory.
Learn More
"Your gut bacteria don't care about diet labels. They care about diversity. Feed them well, and they'll take care of everything else."