William Bulsiewicz

Dr. Will Bulsiewicz (“Dr. B”) is a triple board-certified gastroenterologist and one of the world’s most trusted voices in gut health, dedicated to translating complex microbiome science into practical wellness for millions.

A unique hybrid of researcher and practitioner, Dr. B sits at the intersection of clinical science, public policy, and consumer health innovation. He has published over 25 peer-reviewed studies with more than 5,000 academic citations, and has briefed both the US Congress and the USDA on critical nutrition policy. As the founder of 38TERA, he is actively shaping the future of gut health through targeted product innovation.

Beyond the clinic, Dr. B has sparked a global dietary movement. He is the New York Times bestselling author of Fiber Fueled, The Fiber Fueled Cookbook, and Plant Powered Plus—works that have collectively sold over 500,000 copies and been translated into 20 languages. Leading a highly engaged, global community, he remains a definitive guide on where the science of the microbiome is headed next.