The secretion of growth hormone (GH) and the mass and distribution of body fat are linked through a complex series of interactions. There is increasing evidence that a GH/fat cycle exists and that elements of this cycle may possess regulatory functions. The essential elements of the cycle are: (1) GH-deficient individuals are often obese and lose body fat when they are treated; GH is lipolytic in vitro and causes an acute release of free fatty acids (FFA) when administered in vivo; (3) circulating FFA inhibit the pituitary release of GH by most secretagogues, including growth hormone releasing hormone, and (4) the obese state is characterized by a defect in GH release which can be reversed by weight loss.