RESUMO
Leptin, the product of ob gene expression mainly by the white adipose tissue cells, is a plasma protein hormone appears to act as a key signaling factor for regulating body weight participating in regulation of energy homeostasis. The escalating interest in leptin study is due to its intimate relation to the worldwide prevalent problem of obesity which reached epidemic proportion.Now it's confirmed that one of the main mechanisms of obesity is decreased leptin action. Leptin seems to play dual role in human physiology being subjected to dual control [Caro et al, 1996] under chronic conditions of steady state energy balance, leptin is a static index of the amount of fat stored in the adipocytes, while under non steady state of energy balance situations leptin may be actively regulated by hormonal or nutritional changes