Bariatric surgery is one of the most effective treatments for obesity in adults. Unlike many drugs prescribed to treat obesity, bariatric surgery has a broad range of effects, including physiological impact on the gastrointestinal tract and gut microbiota. In this final installment of our Obesity 2020 webinar series, Lee Kaplan, MD, PhD, will discuss late-breaking research about the role of the gastrointestinal tract and gut microbiota in obesity. He will also review various physiological mechanisms of action of bariatric and metabolic surgery and how they affect the regulation of energy balance and metabolic function.