Vertical sleeve gastrectomy (VSG) is a bariatric surgery that significantly improves obesity and related conditions like type 2 diabetes. This study shows that the benefits of VSG are not due to mechanical restriction of the stomach but are linked to increased bile acids and changes in gut microbial communities. The nuclear bile acid receptor FXR plays a key role in these effects. When FXR is absent, the weight loss and improved glucose tolerance from VSG are reduced. These findings suggest that FXR signaling is essential for the metabolic benefits of VSG. The study also highlights the importance of bile acid signaling and gut microbiota in the success of VSG. The results indicate that FXR signaling contributes to the beneficial effects of VSG by influencing gut microbial communities and metabolic processes. This provides new insights into the molecular mechanisms underlying the benefits of bariatric surgery and suggests potential targets for less-invasive therapeutic interventions.Vertical sleeve gastrectomy (VSG) is a bariatric surgery that significantly improves obesity and related conditions like type 2 diabetes. This study shows that the benefits of VSG are not due to mechanical restriction of the stomach but are linked to increased bile acids and changes in gut microbial communities. The nuclear bile acid receptor FXR plays a key role in these effects. When FXR is absent, the weight loss and improved glucose tolerance from VSG are reduced. These findings suggest that FXR signaling is essential for the metabolic benefits of VSG. The study also highlights the importance of bile acid signaling and gut microbiota in the success of VSG. The results indicate that FXR signaling contributes to the beneficial effects of VSG by influencing gut microbial communities and metabolic processes. This provides new insights into the molecular mechanisms underlying the benefits of bariatric surgery and suggests potential targets for less-invasive therapeutic interventions.