[Causes of obesity].

The aetiology and treatment of obesity requires a knowledge of the mechanisms that control the homeostasis of the fuel substrates and adiposity. The processes of regulation adjust the supply of macronutrients and energy demands with the aim of maintaining a stable body mass. In the light of the most recent research, the hypothesis can be advanced that the control of body weight and its composition depends on an axis integrated by three self-regulated components: appetite, stores thermogenesis and fat deposits. The most important factors involved in obesity seem to be dietary habits diet and physical activity, which are affected by genes, which in their turn affect energy expenditure, the metabolism of energy substrates and food consumption. However, the growing rates of obesity cannot be explained exclusively by genetic causes, since they are in some cases associated with the consumption of diets with a high energy density or rich in fat, and by a growing sedentary life style in society, both in developed and developing countries. The study of genetics and life style involved in the increase of body weight and obesity can facilitate the implementation of preventive actions.