Bariatric-metabolic surgery provides substantial, sustained weight loss and major improvements in glycaemic control in severely obese individuals with type 2 diabetes. I will examine the indications for, and efficacy and safety of, conventional bariatric surgical procedures and their effect on glycaemic control in type 2 diabetes. How often very simple surgical gastrointestinal interventions achieve sustained changes in energy and glucose homeostasis is of great research interest, and understanding is evolving rapidly.

The effect of weight loss appears critical to both short and longer term outcomes and evidence supporting this will be provided. However, there are some clear effects beyond weight loss with some specific anatomical arrangements that are elements of some surgical procedures. The early remission of type 2 diabetes with Roux-en-Y gastric bypass has been of particular interest and a growing array of gastrointestinal changes generated by this procedure is now evident, and many of these changes may influence glucose homeostasis. While very exciting some caution is recommended as the durability of beyond ‘weight loss’ effects is unclear, and there are issues in translating rodent experimental data to humans.

The role of the gut in glucose homeostasis is becoming clearer and could provide insights into the pathogenesis of type 2 diabetes and assist in the development of new procedures, devices and drugs both for obese and non-obese patients.