Their postprandial rise in circulation is blunted in obesity but hyperstimulated postsurgically, so it is reasonable to hypothesize that a RYGB-induced lowering of plasma BCAAs, one of the culprits that impair glucose metabolism and insulin sensitivity, is in part attributable to enhanced GLP-1 and/or PYY signaling. This evidence concerns the gene PYY and obesity due to melanocortin 4 receptor deficiency.