He is board-certified in gastroenterology and internal medicine, and is affiliated with East Cooper Medical Center and Roper St. Francis Mount Pleasant Hospital. He has worked as a gastroenterologist for Lowcountry Gastroenterology Associates in Mount Pleasant, South Carolina, and is a member of the American Medical Association, American College of Physicians, and the American Gastroenterological Association. Bulsiewicz published Fiber Fueled in 2020, and The Fiber Fueled Cookbook Inspiring Plant-Based Recipes to Turbocharge Your Health in 2022. Both books promote a high-fiber plant-based diet that challenges the keto diet and the paleo diet. The books argue that gut health is the key to boosting metabolism, balancing hormones and reducing inflammation and the best way to do this is by consuming dietary fiber from a diverse variety of colourful plants. They also state that dietary fiber fuels gut microbiota which then create short-chain fatty acids.. Bulsiewicz notes that the populations in the Blue Zones consume predominantly plant-based diets, stating, "if you look at the healthiest populations on the planet in modern times, they’re in the five blue zones, and all five blue zones are 90 percent plant based. So, they are not necessarily vegan, but they are plant-predominant in a way where the meat is not the centerpiece. The plant is the centerpiece. The meat is the side show. He recommends fermented foods for gut health such as kimchi and sauerkraut. He follows a plant-based diet in his personal life, in Charleston, South Carolina.
