Over the last few years, the idea of re-purposing bariatric procedures specifically for the treatment of type 2 diabetes (T2DM) has received increasing support by scientific evidence and, consequently, by new clinical guidelines endorsed by diabetes and surgical societies from around the world. There is, however, still some confusion about what defines metabolic/diabetes surgery. A common misconception is that metabolic surgery is defined by the use of novel procedures (i.e. duodenojejunal bypass, ileal interposition or endoluminal approaches), distinct from those traditionally offered for the treatment of morbid obesity or that it would only refer to surgery performed in patients with BMI< 35Kg/m2. In reality, metabolic surgery is defined neither by a specific BMI threshold nor by the type of surgical procedures – in the same way as colon cancer surgery is not defined by the type of colectomy being used. What really characterises metabolic/diabetes surgery is the use of gastrointestinal operations – whatever they are and whatever the BMI – with the specific intent to treat type 2 diabetes (or other established metabolic disease). Hence, traditional Roux-en-Y gastric bypass, sleeve gastrectomy, and biliopancreatic diversion or even laparoscopic adjustable gastric band are all “metabolic surgery” when they are intentionally used to treat diabetes as a primary indication.
The selection of the surgical procedure in metabolic surgery – not unlike in any other fields of surgery – should be based on careful considerations about disease state and severity, mechanisms of action of different procedures, as well as clinical evidence. It is important to note that patients’ motives for surgery and referral patterns can be very different when surgery is offered as a diabetes therapy or as a mere weight loss intervention – this significantly influences the selection of surgical candidates and baseline characteristics of patients populations. Hence, we cannot properly assess the relative efficacy and safety of different operations in patients with diabetes from historical series of “bariatric surgery”. Specific studies of “metabolic surgery” that include patients with the full spectrum of diabetes severity and, ideally, data from randomized trials are crucial before drawing conclusions about the relative efficacy of surgery vs medical therapy and the efficacy and safety of different surgical procedures. Currently, RY-gastric bypass (RYGB), sleeve gastrectomy, gastric banding, and biliopancreatic diversion can all be considered as standard procedures for diabetes surgery, as they all have been assessed in randomized trials against conventional diabetes therapies. These trials also show that a gradient of efficacy and safety across the above procedures exists. Although current evidence shows that RYGB may have the best risk/benefit profile in most patients with T2DM, the choice of the procedure in each patient should be based on an careful and individual assessment of risks and benefits.