Surgical treatment of morbid obesity has been shown to be efficient for long-term weight loss and to improve obesity-related complications. The improvement of type 2 diabetes (T2DM) is dependent of the type of surgery, and is more frequent with gastric bypass than with gastric band. Normalization of glucose metabolism is rapid, often occurring before weight loss, and shown to be related to both a decrease in insulin resistance and an increase in insulin secretion. Some factors limiting the efficiency of gastric bypass on T2DM is the duration of diabetes and the residual beta-cell mass. However, a decrease in diabetes-related death has been found in a large series of surgical cases. These data constitute a good argument for proposing surgery in T2DM obese patients as soon as possible. Nevertheless, whether or not this suggests changing the usual indications for bariatric surgery in T2DM patients, such as a body mass index (BMI) score of<35 kg/m(2), remains controversial.