Energy balance in asymptomatic HIV infection.

Objectives : Body weight is regulated by the balance between energy intake and energy expenditure, but the influence of HIV infection on energy balance has not been fully examined. The main objectives of this study were (1) to assess the effect of HIV on energy balance, (2) to examine the relationship of parameters of immunodeficiency to energy balance, and (3) to examine the interrelationship of different components of energy balance in asymptomatic HIV-seropositive men. Design : A cross-sectional study of nutrition and metabolism in asymptomatic HIV-seropositive men. Methods : Components of energy balance were examined in 104 asymptomatic HIV-seropositive men (CD4 count 4-482x10 6 /l) and 57 age-matched HIV-seronegative male controls. Energy and protein intake were measured using 5-day diaries, and small bowel absorption and permeability was assessed using four sugar probes. Resting energy expenditure was calculated from indirect calorimetry and nitrogen loss estimated from 24 h urine collection. Four methods were used to assess the effect of HIV infection on body composition (anthropometry, dual energy X-ray absorptiometry, bioelectrical impedance and 24 h urine creatinine). Results : Resting energy expenditure per kilogram of fat-free mass was raised (P< 0.0001), fat mass was decreased (P= 0.001), fat-free mass was increased (P = 0.05), energy intake was higher (P = 0.05), absorption of L-rhamnose (P = 0.01) and 3-O-methyl-D-glucose was decreased (P = 0.003), and small bowel permeability was increased (P < 0.0001) in HIV-seropositive men compared with HIV-seronegative controls. HIV-seropositive subjects with a CD4 count less than 100x10 6 /l had decreased absorption of L-rhamnose (P < 0.05), D-xylose (P < 0.05) and 3-O-methyl-D-glucose (P < 0.05) compared with HIV-seropositive subjects at higher CD4 counts, and had a similar resting energy expenditure to HIV-seronegative controls. Protein intake, carbohydrate, fat and protein oxidation, 24 h nitrogen excretion and appendicular muscle mass were similar in HIV-seropositive men and controls. Conclusion : HIV infection exerts a direct effect on parameters of energy balance that varies with the severity of immunosuppression.