The insulinotropic effect of the incretin hormones, glucose-dependent insulinotropic polypeptide (GIP), and glucagon-like peptide-1 (GLP-1) is impaired in patients with type 2 diabetes. It remains unclear whether this impairment is a primary pathophysiological trait or a consequence of developing diabetes. Therefore, we aimed to investigate the insulinotropic effect of GIP and GLP-1 compared with placebo before and after 12 d of glucose homeostatic dysregulation in healthy subjects.