It has been proposed that differences in the secretion of gut hormones (ghrelin, GLP-1, peptide YY) occurring after SG or RYGB may play a pivotal role in diabetes regression by acting on appetite [41, 42], improving insulin sensitivity, and restoring the first phase of insulin secretion [23, 27, 28], all effects which, concomitantly to weight loss, participate to the improvement of diabetes. The gene discussed is INS; the disease is diabetes mellitus.