NPY and Other metabolic disease: 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.