Bariatric (weight loss) surgery is currently considered the most effective treatment for extreme obesity. However, the long-term effects of bariatric surgery on weight loss, physical health, and psychological health are highly variable. In collaboration with our colleagues at the Bariatric Surgery Program at Toronto Western Hospital, we study the psychosocial aspects of bariatric surgery. Current studies are examining psychosocial predictors of bariatric surgery outcome, psychosocial adjustment following bariatric surgery, and stigma regarding bariatric surgery. We are also developing evidence-based psychosocial treatments for bariatric surgery patients with the aim of improving bariatric surgery outcomes.