Bariatric surgery is an effective treatment for morbid obesity, which is increasingly recognized as a familial disease. Healthy behavior transmission may be enhanced by family relationships.Objective: To determine changes in weight and healthy behavior in patients who underwent Roux-en-Y gastric bypass surgery and their family members.Design: Prospective, longitudinal, and multidimensional health assessment before and 1 year after index Roux-en-Y gastric bypass surgery.