Studies of Body Composition in Patients with the Acquired Immunodeficiency Syndrome

1 The acquired immunodeficiency syndrome (AIDS)is the most serious worldwide public health problem of the current generation. While knowledge of the disease has advanced rapidly, no effective means of halting its spread through the population or of halting its progression in the body have been identified. Treatment of people affected with this multi-system disorder is limited by incomplete knowledge of its pathogenesis. Elucidation of the mechanisms of the disease’s progression should lead to improvements in treatment and in the length and quality of life of AIDS patients. Protein-energy malnutrition (PEM) is a common complication of AIDS [1, 2] and contributes significantly to its morbidity and mortality. Our laboratory has studied PEM in AIDS patients since 1981 with the aims of characterizing the alterations in body composition that occur, identifying the pathogenetic mechanisms underlying PEM, demonstrating the functional consequences of PEM, and determining the efficacy of nutritional support in promoting body mass repletion. In this review, we will summarize the status of our studies of body composition in patients with AIDS and attempt to establish a framework for future investigations of the nature and treatment of PEM in AIDS. The core of our nutritional assessments has been the estimation of body composition. These studies, performed in the Body Composition Laboratory at St. Luke’s Hospital, involve measurement of total body potassium (TBK) content by whole body counting of 40K, as well as determination of total body water and extracellular water volumes by isotope dilution techniques, and body fat content by anthropometric measurements [2-6]. Total body potassium content is a well accepted measure of body cell mass, and its measurement correlates well with calculations of intracellular water volume, another valid parameter of body cell mass. 1. Our initial studies demonstrated that malnutrition in AIDS is common, severe, and progressive [1]. A group of 33 AIDS patients was shown to have diminished TBK and intracellular water volume compared to homosexual and heterosexual controls, indicating body cell mass depletion (table 1) [2]. The depletion of TBK in the AIDS group was greater than expected from analysis of body weight because of the relative expansion of the extracellular water volume and the ratio of extracellular to intracellular water. Variably severe hypoalbuminaemia was found in the AIDS patients. The depletion of TBK was shown not to be related to overt adrenal dysfunction. The severity of depletion was related to length of survival, as patients surviving less than three months were significantly more depleted than those who survived more than six months after study. On the other hand, body fat content was quite variable and patients with significantly decreased TBK were seen who had subnormal or elevated body fat contents. These findings are consistent with studies of body composition in other models of PEM [7-9] and provide an adequate cross-sectional description of body composition in AIDS. TABLE 1. Cross-sectional study of body composition in AIDS patients