GCG and type 2 diabetes mellitus: Recent reports using elegant study designs have suggested “a significant role” for GLP-1 in resolution of T2D after RYGB [23, 24], although several reviews [18, 20, 21] attribute only some or none of the antidiabetic effects to GLP-1, consistent with mouse studies in which GLP-1 was not required for either T2D resolution or weight loss after RYGB [25, 26].