Thus, in order to investigate the potential association of endocannabinoids and gastrointestinal peptides, specifically, ghrelin, PYY and CCK, with hedonic eating in PWS, we have measured here changes in the circulating levels of these appetite-regulating substances before and after the exposure to and consumption of chocolate, a well-known highly palatable food, in satiated PWS patients. This evidence concerns the gene PYY and Prader-Willi syndrome.