Laparoscopic adjustable gastric banding (LAGB), laparoscopic Roux-en-Y gastric bypass (RYGB) and laparoscopic sleeve gastrectomy (SG) are the three most commonly performed bariatric procedures. Obesity responds well to bariatric surgery, with major long-lasting weight loss that is most pronounced after RYGB and SG, where the mean weight loss is about 40 kg or 15 body mass index (BMI) units. Some of the benefits after RYGB and SG are independent of weight loss, and the remission of type 2 diabetes is observed a few days after the operation; this depends on changes in insulin sensitivity and gut hormone responses, especially a 10-fold increase in glucagon-like peptide-1 (GLP-1), which improves insulin secretion. After gastric banding, the remission of diabetes depends more on weight loss. Bariatric surgery reduces cardiovascular risk factors including hypertension, lipid disturbances, non-alcoholic fatty liver, musculoskeletal pain and reduces mortality of diabetes, cardiovascular diseases and cancers. Bariatric surgery also improves quality of life. The acute complications of surgery are infection, bleeding and anastomotic leak. Long-term complications are nutritional deficiencies, including vitamins and minerals, and anemia. Some patients have dumping after meals, and a few patients will develop postprandial hypoglycemia after RYGB. About 25% of patients require plastic surgery to provide relief from excessive skin tissue.