INS and diabetes mellitus: At least for the prevention of progression to diabetes, several mechanisms are involved; in a tentative list, we should include a reduction of insulin resistance for all BMS, together with a decrease of body fat, and the overall percentage of visceral fat [113]; for Roux-en-Y (RYGB) and for biliopancreatic diversion (BPD), additional factors might be involved, such as an increased secretion of gastrointestinal hormones, not directly related to weight loss, with the possible improvement of insulin release [114,115].