HUMAN EATING - EVIDENCE FOR A PHYSIOLOGICAL-BASIS USING A MODIFIED PARADIGM

The aim of these studies was to determine if meal requests and changes in hunger ratings in humans were related to spontaneous changes in bl ood glucose concentration. In our first study, 18 healthy subjects wer e acutely isolated from food and time cues. Blood glucose was continuo usly monitored online and visual analog ratings of hunger were obtaine d following an overnight fast. Spoken meal requests, if they occurred, were also recorded. In 83% of the subjects, both the perception and b ehavioral expression of hunger, as assessed by changes in hunger ratin gs and meal requests, were preceded by, and correlated with, brief, tr ansient declines in blood glucose (nadir: -10% at 27 min). The pattern , magnitude and time course of these declines was similar to those obs erved in rats. This significant association, between increased express ion of hunger and declines in blood glucose, is being tested in a seco nd, ongoing study using acute insulin infusions to mimic spontaneous t ransient declines in blood glucose. Each subject was studied twice: ei ther insulin or saline was infused while hunger ratings were obtained. Preliminary results in five subjects indicate that hunger ratings inc reased after insulin-induced transient declines in blood glucose. No c hange in hunger ratings occurred when blood glucose concentration was stable. These results suggest that this temporal pattern of blood gluc ose reflects an antecedent physiological event or provides a signal re lated to the expression of hunger in humans. Further understanding of human eating may result from investigation of the complex interaction of physiological and other factors in an experimental setting that all ows the expression the behavior under study.