ii) plasma glucagon levels and ISRs both increase for the first 30 minutes after ingestion of a liquid mixed meal in humans with normal glucose tolerance, impaired glucose tolerance, and type 2 diabetes mellitus [15]; and iii) the paradoxical postprandial increases in both insulin and glucagon levels are greatly exaggerated in humans with prior Roux-en-Y gastric bypass [32]. This evidence concerns the gene GCG and type 2 diabetes mellitus.