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Will Bulsiewicz, MD, MSCI

Co-Founder and Co-CEO
38TERA
Charleston, South Carolina, United States

Will Bulsiewicz, MD MSCI (known as “Dr. B”) is an award-winning gastroenterologist, gut health expert, and New York Times bestselling author. Dr. B received his medical degree from Georgetown University and a master’s in clinical Investigation from Northwestern University. He earned the highest clinical honors in both his residency at Northwestern and his gastroenterology fellowship at UNC—recognition reserved for the top physician in each graduating class. He also completed an NIH-funded fellowship in epidemiology at UNC. He has authored more than twenty-five scientific papers, his work has been cited over 5,000 times by other scientists, and he has delivered numerous keynotes as well as briefings to Congress, the USDA, and the NFL Alumni. His books Fiber Fueled and The Fiber Fueled Cookbook have sold over 500,000 copies and are translated into 20 languages. His highly anticipated third book, Plant Powered Plus, is scheduled for publication on January 13, 2026.

As Co-Founder and Co-CEO of 38TERA, Dr. B works alongside nutrition scientist and author Simon Hill to develop gut health supplements that are clinically informed, microbiome-supportive, and designed for real-life use. Together, they’re raising the bar within the supplement industry by prioritizing not only clinical effectiveness, but also transparency, safety, and integrity in a space that has historically lacked regulation and accountability. Dr. B also serves as the U.S. Medical Director of personalized nutrition company ZOE, where he helps translate cutting-edge microbiome science into practical, personalized insights for better health. Through these roles, he continues to shape the gut health landscape from both the research and product sides, driving meaningful, real-world impact. He lives in Charleston, South Carolina with his wife and four kids and offers free resources at theguthealthmd.com.

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