Although we cannot exclude the fact that the effect of the incomplete antagonism of Y2-receptors due to the fluctuation of the drug concentration may influence the results of this study, it seems that on a regular chow diet, independent of normal or excess NPY, Y2-receptors accessible to a peripherally administered Y2-receptor antagonist seem to be beneficial to energy metabolism, and their blockage leads to weight gain and metabolic disorders possibly via centrally decreased sympathetic activity. This evidence concerns the gene NPY and metabolic disease.