ENERGY-EXPENDITURE AND WASTING IN HUMAN-IMMUNODEFICIENCY-VIRUS INFECTION

Background. Increased expenditure of energy at rest has been considere d a contributing factor to the negative energy balance and weight loss that occur in patients with human immunodeficiency virus (HIV) infect ion. However, the true determinant of energy balance is not resting bu t total energy expenditure. We sought to determine the contribution of total energy expenditure to weight changes in patients with HIV-assoc iated wasting. Methods. We performed 51 assessments of energy metaboli sm in 27 men with HIV infection at different stages of disease, includ ing periods of both rapid and slow weight loss. Resting energy expendi ture was measured by indirect calorimetry, total energy expenditure by the doubly-labeled-water technique, and energy intake by recording th e weight of food consumed. The results were compared with the rate of weight loss or gain. Results. The mean (+/-SD) total energy expended b y the HIV-infected men was 2750+/-670 kcal per day, no more than that expended by normal men. There was a significant positive relation betw een total energy expenditure and the rate of weight change (r=0.61, P< 0.001); thus, during rapid weight loss, total energy expenditure was r educed to 2180+/-580 kcal per day (P = 0.009), primarily because of re duced physical activity. During rapid weight loss, the negative energy balance (-8501+/-580 kcal per day) was primarily the result of the re duction in energy intake, to 1330+/-610 kcal per day; intake correlate d strongly with the rate of weight change (r=0.84, P<0.001). Conclusio ns. In patients with HIV infection, total energy expenditure is reduce d during episodes of weight loss. Reduced energy intake, not elevated energy expenditure, is the prime determinant of weight loss in HIV-ass ociated wasting.