GLP-1, OXM, and PYY levels achieved following GOP and 0.9% saline infusion. (a) GLP-1 levels. Peak postprandial levels of GLP-1 in RYGB group matched by GOP infusion. (b) OXM levels. Peak postprandial levels of OXM in RYGB matched by GOP infusion. (c) Total PYY levels. Peak postprandial levels of PYY in RYGB matched by GOP infusion.