Most reports investigating the hormonal and metabolic effects of bariatric surgery studied obese subjects after partial weight loss only. Nevertheless, all studies showed significant improvements of insulin secretion, action, clearance and inhibition of its own secretion, although the parallel kinetics of all these changes remained questionable. Using the intravenous glucose tolerance test, we demonstrated a full normalization of insulin secretion, action on glucose metabolism and clearance in eight obese women who recovered and maintained ideal body weight following gastroplasty. Reciprocal changes were observed between postglucose acute insulin secretion and insulin-mediated glucose disposal so that the so-called disposition index (product of these two variables) remained unchanged after vs before gastroplasty in those individuals with normal glucose tolerance. These favourable results should encourage obtaining a drastic and sustained weight loss in patients with severe obesity at risk of developing type II diabetes.