Changes in Energy Expenditure Resulting from Altered Body Weight

Abstract

Background No current treatment for obesity reliably sustains weight loss, perhaps because compensatory metabolic processes resist the maintenance of the altered body weight. We examined the effects of experimental perturbations of body weight on energy expenditure to determine whether they lead to metabolic changes and whether obese subjects and those who have never been obese respond similarly. Methods We repeatedly measured 24-hour total energy expenditure, resting and nonresting energy expenditure, and the thermic effect of feeding in 18 obese subjects and 23 subjects who had never been obese. The subjects were studied at their usual body weight and after losing 10 to 20 percent of their body weight by underfeeding or gaining 10 percent by overfeeding. Results Maintenance of a body weight at a level 10 percent or more below the initial weight was associated with a mean (±SD) reduction in total energy expenditure of 6±3 kcal per kilogram of fat-free mass per day in the subjects who had never been obese...