Effects of body weight and food intake on pleasantness ratings for a sweet stimulus.

A physiological role for pleasure has been suggested from observations that glucose loads reduced pleasantness ratings for sweet stimuli in normal weight but not in weight-reduced subjects. This hypothesis was reexamined in fasting and food-loaded, lean and obese subjects. Magnitude estimates of sweetness and pleasantness were obtained for seven sucrose concentrations. Indices of obesity including percent overweight, percent body fat, and body mass index were calculated. Pleasantness ratings of fasting subjects either increased up to a moderate concentration and then declined (type I hedonic response) or increased monotonically with concentration (type II hedonic response). Both types of response were found in lean and obese subjects. Within each weight group there appeared a negative correlation between pleasantness response and indices of obesity. Caloric loads reduced hedonic ratings of type II lean and obese subjects, but did not affect pleasantness response of type I lean and obese subjects. These findings indicate the presence of an hedonic monitor biased by body weight and caloric intake. The data suggest a physiological role for pleasure in regulating body weight at different set points in lean and obese subjects.