Energy Metabolism in Human Obesity

ABNORMALLY HIGH fasting levels of plasma free fatty acids (FFA) and decreased responsiveness of this lipid fraction to various lipolytic stimuli in obese humans and animals have now been documented by several investigators.1-5Whether such alterations in FFA metabolism relate to obesity as cause or effect, however, remains speculative. We have previously reported the failure of the plasma FFA to rise significantly during periods of prolonged fasting in certain patients with longstanding, therapeutically resistant obesity.1In contrast, a normal FFA response to fasting has been observed in patients whose obesity seems clearly the result of compulsive overeating. In the present investigation, the plasma FFA response to the more potent lipid-mobilizing action of epinephrine is compared in obese subjects and normal weight controls in two separate experiments: an initial study in which plasma FFA and glucose levels were determined before and 30 minutes after epinephrine administration, and a subsequent