Peptide YY (PYY), a novel 36 amino-acid amidated hormone is a component of the complex neuroendocrine control process. This gut hormone (3-36), when infused into subjects, has been shown to reduce food intake in normal-weight and obese individuals. PYY (3-36) infusion also reduces the plasma levels of the hunger-promoting hormone ghrelin. PYY (3-36) levels have been shown to drop pre-meal and then increase post-prandially. In circulation, PYY (3-36) exists in at least two molecular forms: (1-36) and (3-36). PYY (3-36) selectively binds to Y2 receptors, and it has been found in human intestine and circulating blood.