The Exam Room by the Physicians Committee Fix Your Gut Naturally: Dr. Will Bulsiewicz on Fiber Maxing and Building Healthier Microbiome
Nov 13, 2025
Dr. Will Bulsiewicz, a gastroenterologist and microbiome expert, joins the discussion on unlocking better gut health. He dives into the concept of fiber maxing, advocating for gradual dietary changes, and shares the benefits of resistant starch found in cooled potatoes. The conversation explores how exercise can enhance gut microbiota and the impact of artificial sweeteners on gut health. Additionally, he emphasizes the importance of diversity in the microbiome and shares insights from his upcoming book, Plant Powered Plus.
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Leftover Starches Boost Gut Microbes
- Resistant starch forms when starchy foods cool and behaves like fiber by feeding different colon microbes.
- It reaches further into the colon and supports microbes starving in other regions.
Gradually Build Fiber Intake
- Start low and go slow when increasing fiber to avoid discomfort and bloating.
- Build toward goals like two cups of beans per day over weeks to months based on your starting point.
Use Feedback And Timeframes
- Use a rule-based approach: monitor your body's feedback and adjust fiber increases accordingly.
- Expect meaningful microbiome changes within about four weeks if you progress steadily.
