In order to understand the underlying mechanisms by which weight loss surgeries improve metabolic profiles in type 2 diabetes mellitus (T2DM) patients and to evaluate the relevance of the length of the common limb in modulating various aspects of metabolism, we performed regular duodenal-jejunal bypass (DJB) and long-limb DJB (LL-DJB) surgeries in Goto-Kakizaki (GK) rats and compared their effects on glycemic control.