PYY and obesity due to melanocortin 4 receptor deficiency: PYY(3–36) is currently under investigation for use in the treatment of obesity, and it also suppresses appetite4,9,13,24 Interestingly, exaggerated secretion of GLP-1 and PYY(3–36) occurs in some gastric bypass (RYGB) surgery patients, and these alterations correlate with long-term appetite suppression and weight-loss that is associated with such surgery25.