Metabolic and behavioral differences between dieting and intestinal bypass.

The present studies were designed to compare physiological and behavioral changes produced by weight loss induced with dieting and the weight loss which follows intestinal bypass. A group of 7 grossly obese individuals were hospitalized in a metabolic unit and studied at their initial weight after 4 weeks on a hypocaloric diet and again following a comparable weight loss after intestinal bypass surgery. The score indicating depression increased after dieting, but returned to initial levels after bypass. A number of other behavioral changes were recorded including a reduction in the time spent thinking about food, the time when the individual felt hungry and a greater percentage of time when they felt "full". After bypass, the patients also selected and ate smaller quantities of food. There were no metabolic differences following the period of dieting. Among the metabolic changes after bypass were an increase in glycerol and a decrease in insulin. The possible relationships between the metabolic and behavioral changes have been reviewed.