High Quality Content by WIKIPEDIA articles! Bariatric surgery, or weight loss surgery, is a type of procedure performed on people who are dangerously obese, for the purpose of losing weight. This weight loss is usually achieved by reducing the size of the stomach with an implanted medical device gastric banding or through removal of a portion of the stomach gastric bypass surgery. Long-term studies show the procedures cause significant long-term loss of weight, recovery from diabetes, improvement in cardiovascular risk factors, and a reduction in mortality of 23% to 40%. The U.S. National Institutes of Health recommends bariatric surgery for obese people with a body mass index BMI of at least 40, and for people with BMI 35 and serious coexisting medical conditions such as diabetes.