Indeed, marked weight loss achieved through bariatric surgery is associated with improvements in glucose levels and cardiac structure and function in patients with obesity and T2DM.14, 15, 16 Clearly, bariatric surgery results in very substantial weight loss, but ancillary effects also have been described, such as incretin response and changes of the gut microbiome, and some refer to bariatric surgery as metabolic surgery.17 Here, GCG is linked to obesity due to melanocortin 4 receptor deficiency.