A general model of intake regulation.

Previously proposed models of intake regulation focus on specific variables thought to influence overall intake, and include factors involved in negative feedback loops with intake as well as genetic influences on intake. Recent evidence, however, suggests that these models although informative, are incomplete. They cannot account for the observations of prolonged and increasing deviations from defended levels, weakness and transitoriness of compensatory responses, the presence of powerful factors that are not compensated, and behavioral genetic data suggesting that there are a wide variety of independent genetic influences on numerous factors that influence intake. As a result we propose a new general model of intake regulation in which intake is influenced by both a set of uncompensated factors that are not influenced by intake and by a set of compensated factors that are. The preferred levels of intake and both sets of factors are specified as influenced by heredity. Further, the model includes impact factors, weights, which specify the magnitude of the effect each factor has on intake. The weights are assumed to be different for different individuals and their values are determined by heredity. A computer simulation of the new model demonstrated that it maintains different levels depending upon the external and internal environments, that changes in these environments result in new levels, and that inherited individual differences in responsiveness to these factors can markedly influence the levels obtained. The proposed general model appears to fit existing knowledge and is parsimonious and widely applicable. Future work should be directed to testing the general model and further developing specific models within the conceptual framework employing known physiological systems and uncompensated stimuli. Copyright 2002 Elsevier Science Ltd.