Morbid obesity has become a health crisis in the United States. Medical programs developed at nonoperative attempts to lose (and maintain) an adequate weight loss are largely unsuccessful. Bariatric surgery has been proven to be effective at inducing and maintaining a satisfactory weight loss to decrease weight-related comorbidity. Bariatric operations include procedures that decrease mechanically the volume capacitance of the proximal stomach (vertical banded gastroplasty, laparoscopic gastric banding) or decrease the proximal gastric capacitance and establish a partial selective malabsorption (gastric bypass and its modifications, partial biliopancreatic bypass, and duodenal switch with partial biliopancreatic bypass). These operations should induce a loss of at least 50% (or more) of excess body weight. Not all patients are candidates for these procedures, and the best results are obtained by a multidisciplinary team (including nutritionist, physician, dietitian, psychologist or psychiatrist interested in eating disorders, and surgeon).