In obese patients with type 2 diabetes (DM2) insulin resistance often hampers adequate regulation of blood glucose levels.

Weight loss improves glucose regulation and decreases insulin resistance, but is often difficult to sustain with drugs or diet.

Bariatric surgery induces substantial and sustained weight loss, on average > 50% of excess weight. It also lowers blood glucose levels.

The effect on glucose regulation occurs within a week of surgical procedures that prevent food being absorbed in the proximal intestine, such as gastric bypass or biliopancreatic diversion.

The effect might be explained by a faster delivery of food to the ileum, leading to enhanced secretion of glucagon-like peptide-1 and other intestinal hormones that stimulate insulin secretion. Prevention of food absorption in the duodenum also seems to play a role.

Bariatric surgery is a good therapeutic option for a selected and motivated group of obese patients with inadequately controlled DM2.