Eating in the laboratory: behavioural aspects of the positive energy balance

A survey is made of a number of experiments conducted in our laboratory over the last six years. Our working hypothesis assumes that positive energy balance, which should not be prematurely defined as the cause of obesity, is itself caused by disturbances in appetite and satiation control which, given certain environmental conditions, can favour the occurrence of obesity. Three points are considered: (1) The hyperphagic reaction as a response to stress. The experimental findings suggest that the hyperphagic reaction is not primarily a biologically determined phenomenon but rather a learned response. The hyperphagic reaction is found more frequently in female and overweight persons. Most children react to stress with a decrease in food consumption. (2) Disturbances of satiation control. The food intake of obese Ss has a linear time function, whilst children and normal weight adults reveal a biological, negatively accelerated satiation curve. (3) Increased responsiveness to external cues. The concept of externality is extended to include the aspect of an internal-external stimulus discrepancy. The findings show that not only manifest obese Ss but also latent obese Ss are characterized by an increased responsiveness to external cues. In three different experiments with the same Ss it could be demonstrated that externality is to a greater or lesser extent independent of the experimental procedure. Finally, methodological aspects are discussed, because in studies on human appetite the possibility exists that experimental procedure, sample composition and laboratory conditions can exert a direct influence on the results.