A simulation model of psychobiosocial theory of human food-intake controls.

Over 15 years ago, a psychobiosocial theory of appetite was formulated in the light of experimental evidence from rats and people that appetite was suppressed by the flow of energy to lean body mass and that much ingestion was a learned response to integrated dietary, somatic and social cues. Enough was known in 1973 about these influences on food intake and about rates of flow of energy-yielding substrates around the body of the rat to program a computer simulation which had no loose parameters. This rat model successfully predicted feeding patterns under a variety of normal and abnormal conditions, including the day-night meal rhythm, the overeating and obesity following ventromedial hypothalamic lesions, and the suppression of appetite by fenfluramine via slowed gastric emptying. In 1976, its parameter values were adjusted to those expected for an adult person having food freely available and a sedentary lifestyle. The output of this human model was remarkably realistic in meal pattern: culture appears to adapt to the physiological average. The predicted effect on appetite of energy released from adipose in proportion to the energy stored was relatively minute but very persistent. These old results are no less relevant now to improvement of our understanding of human food-intake controls and to more effective reduction and prevention of unhealthy overweight.