The 33-amino-acid peptide NPY, which is the most potent stimulant of food intake known, is produced by cell bodies in the ARC with axons that project to the PVN (which is thought to be the main site of its action). Centrally administered NPY causes hyperphagia with a preference for carbohydrates and promotes increased fat storage and obesity by reducing the activity of the sympathetic nervous system and by increasing the expression of LPL in white adipose tissue.22 Among several influences, there is evidence that the hypothalamic NPY system is negatively regulated by insulin, leptin, and CRH and positively regulated by glucocorticoids.14,17,23,24 NPY activity is increased in conditions associated with energy deficiency, such as caloric restriction, lactation, and intense exercise.
This response seems to be mediated by reduced negative feedback from insulin and leptin and positive feedback from glucocorticoids.