Gastrointestinal (GI) operations originally used for the treatment of ulcers/cancer or morbid obesity (bariatric surgery) can cause major improvement of glucose metabolism and durable remission of type 2 diabetes. Experimental evidence from animal and human studies show that such effects are at least in part independent on weight loss and directly result from changes in the anatomy and physiology of the GI tract. These findings provide a biological rationale for repurposing GI operations as a treatment for diabetes itself, a practice referred to as metabolic surgery Numerous randomized clinical trials comparing surgery vs conventional medical therapies and lifestyle intervention for type 2 diabetes now show that metabolic surgery can achieve prolonged disease remission or major glycemic improvements, as well as reduction of medication usage and cardiovascular risk in overweight and obese patients. On the back of such evidence, the 2nd Diabetes Surgery Summit (DSS-II), an international consensus conference, recommended that metabolic surgery be considered as a treatment option for type 2 diabetes in patients with BMI >30Kg/m2 or >27.5Kg/m2 in case of Asian ethnicity. The DSS-II recommendations and guidelines are currently endorsed by over 50 international organizations including the Australian Diabetes Society and other leading diabetes, endocrinology and surgical societies. In January 2017, the American Diabetes Association has incorporated the DSS-II recommendations in their Standard of Medical Care. Over the past decade, efforts to explain how surgery on the gut controls diabetes have identified several potential mechanisms. Changes in gut hormones, bile acids, intestinal glucose transport and metabolism, microbiota and nutrient sensing appear to contribute. Emerging evidence also suggest surgery may tackle dysfunctional GI mechanisms that contribute to diabetes pathophysiology. This presentation illustrates the DSS-II guidelines as well as their supporting biological and clinical evidence.