HOW CAN EATING BEHAVIOR BE REGULATED IN THE COMPLEX ENVIRONMENTS OF FREE-LIVING HUMANS

The eating behavior of humans in their natural environments is complex ly affected by a myriad of nutritional, physiological, psychological, sociological and cultural factors. We have employed the diet diary tec hnique to document the influence of: the subjective states of hunger, the amount of food or fluid remaining in the stomach at the onset of i ngestion, and its composition, the time of day, day of the week, phase of the moon, month of the year, the location, the number of other peo ple present, the relationship of eating companions to the subject, die tary restraint, and eating disorders. Recently we have demonstrated, w ith twins, significant heritabilities for the amounts of foods and flu ids ingested, independent of body size. By viewing behavior in freeliv ing conditions the relative importance of these factors in the determi nation of the amounts and timing of intake can be discerned and measur ed. The analysis indicates that immediate environmental psychological, social, and cultural stimuli exert powerful but short-lived effects o n intake. Physiological stimuli, on the other hand, appear to influenc e intake subtly but persistently. Their influences are difficult to do cument on the short-term, but clear over long periods of time. Short-t erm intake for the most part would appear to be unregulated and allowe d to vary spontaneously within a relatively wide range. Physiological variables appear to feed back after a delay of at least a day and usua lly longer to alter the overall level of intake bias. The persistent b ias continues to shift intake, producing a cumulative net alteration o f intake, while the effects of random short-term influences average ov er time, and result in no net effect on intake.