[Multifactorial etiology of obesity: nutritional and central aspects]

World-wide obesity and its effects are public health problems. Research on way of life and eating habits give some indications of etiological factors. Breast feeding and quantity of proteins intake in formulas are factors influencing the risks of obesity later on in life. Research undertaken by Rolland Cachera shows us the importance of the curve of BMI and how the obesity rebound can be predictive of obesity in later years allowing early decisions of weight control. Energy intake and energy expenditure are regulated by the central nervous system. It is a complex mechanism of afferent and efferent systems through the hypothalamus. The inverse effects of ghreline and of leptine on energy balance are more and more studied and cases of precocious obesity are explained by the identification of rare forms of monogenic obesity linked to the metabolism of leptine. The importance of inherited genes has a role and genetic predisposition is a reality. This new approach allows a clinical, etiological and, in the future, probably therapeutic attitude in case of severe precocious obesity.