[Mechanisms of regulation of energy balance]

To establish energy balance, the three distinct terms of the balance must be precisely defined and measured. These terms are: the energy input by food intake, energy expenditure as heat and the body energy content in the form of lean and fat masses. The constancy of this fat store, generally associated with that of body weight, is an indication of the balance between energy intake and the sum of expenditure and non-lipidic energy retention. This balance is only carried out at medium or long-term. It results from the initiation of mechanisms regulating strongly positive or negative short-term balances between gains and losses. Four possible models of this regulation are presented and discussed using experimental data. A number of works is reported, demonstrating the role played by two complementary mechanisms of regulation. The first one is neuroendocrine mechanism controlling food intake and adjusting it to the input and output of glucose in the blood compartment. The second one is an autonomous mechanism regulating the body fat mass. It corrects, at medium and long-term, the filling and depletion of the adipose compartment which result from imbalances in the overall energy balance. This mechanism indirectly affects food intake in a regulatory sense. It is neurally controlled by the sympathetic and parasympathetic nervous system and governed by the medioventral nuclei of the hypothalamus.