A recent study pointed out that GIP infusion was able to stimulate insulin secretion in the lean, obesity or obesity patients with impaired glucose regulation (IGR) rather than obesity patients with T2DM, whereas resulted in the anabolic effect (that means exaggerated fat deposit) in obesity patients with T2DM, indicating the blunted insulinotropic but preserved lipogenic actions in obesity patients with T2DM.25 To date, it is difficult to dissect the separate contributions of insulin and GIP to glucose and lipid metabolism. The gene discussed is GIP; the disease is obesity due to melanocortin 4 receptor deficiency.