The incidence of obesity is rapidly increasing all over the world in epidemic proportions.The epidemia now affects young children and accumulative evidences suggest that the origin of the disease may occur during foetal development and early life. This has introduced the concept of "developmental programming" supported by experimental studies in animal models and numerous epidemiological data. This concept supports the idea that nutritional and hormonal status during pregnancy and early life could interfere irreversibly on the development of the organs involved in the control of food intake and metabolism and particularly the hypothalamic structures responsible of the establishment of the ingestive behaviour and regulation of energy expenditure. The mechanisms responsible of this developmental programming remain poorly documented. However, recent research indicate that the adipokine leptin plays a critical role in this programming.