[Autoregulation of body weight and body composition in man. A systematic approach through models and simulation].

The regulation of body weight and its composition in humans is examined from the standpoint of system analysis. It is based upon the hypothesis that the ultimate purpose for modulating body energy stores is to ensure the maximum duration for survival of the individual in the face of calorie deficit. A mathematical model, which is built on this hypothesis, allows quantitative simulation of variations in body weight and composition which occur during cycles of underfeeding/refeeding, and is achieved with the use of three global parameters. One of them controls the partitioning of body energy stores between fat and lean tissues, and the other two are concerned with the control of adaptive thermogenesis. The first of these two parameters for thermogenesis modulates the efficiency of fat storage by a function which is inversely proportional to the level of replenishment of the adipose tissues, and the other one controls regulatory thermogenesis which is a direct function of energy imbalance. These two forms of adaptive thermogenesis operate independently of each other and their amplitude depends upon the nutritional background of the individual. This model can be used as a theoretical framework for integrating numerous data in the literature on physiological processes that are involved in the regulation of body weight and body composition.