The U.S. Centers for Disease Control and Prevention

The U.S. Centers for Disease Control and Prevention (CDC) recognized wasting as an AIDS-defining condition in 1987. The "wasting syndrome" is defined as a weight loss of at least 10% in the presence of diarrhea or chronic weakness and documented fever for at least 30 days that is not attributable to a concurrent condition other than HIV infection itself.(1) In practice, any involuntary weight loss of that magnitude is typically considered wasting.

A significant relationship between weight loss and mortality, disease progression, or both has been demonstrated in numerous prospective and retrospective studies both before the advent of effective antiretroviral therapy (ART) (2-11) and in the current era of treatment, in regions where such therapy is available.(12,13) In addition to weight loss, depleted levels of body cell mass, which contains the metabolically active tissue, have been associated with increased risk of mortality in patients with HIV infection.(2,5,6) It is important to note that death from malnutrition in patients with AIDS occurred at the same degree of depletion of weight and body cell mass (66% and 54% of normal, respectively) (2) as was seen in historical reports of death from starvation.(14,15) Body mass index (BMI; see www.cdc.gov/nccdphp/dnpa/bmi/index.htm), calculated by dividing an individual's weight in kilograms by the square of his or her height in meters, also has predictive value. Evaluation of data from a large French cohort studied between 1985 and 1997 found hazards ratios for death of 2.2 and 4.4 for BMIs of 16.0-18.4 and <16.0 class="sup">2, respectively, after adjusting for other factors that affect mortality (p < .0001 in each case).(11) In this same study, weight losses of <5%,>10% were associated with hazards ratios for death of 1.9, 3.3, and 6.7, respectively (p < .0001 in each case).

The prevalence of wasting as an initial AIDS-defining diagnosis was estimated to range up to 37% in surveys performed before the advent of effective ART.(16-22) Some reports suggest that the incidence of wasting has declined since the introduction of effective ART,(22,23) but data from other studies indicate that wasting remains a significant complication, even in populations with widespread access to effective ART.(24-26) A recent report from a large cohort study suggested that although weight loss is an infrequent occurrence, a more gradual, progressive loss of lean tissue continues in many subjects.(27) Moreover, although weight gain (28-30) and increased muscle protein synthesis (31) may occur with initiation of ART, lean tissue is not consistently restored.(28)

Weight loss in HIV infection is characterized by depletion of both fat and lean tissue.(32-39) Rapid weight loss has been associated with acute infections,(40,41) whereas more gradual weight loss has been associated with malabsorptive disorders.(41) Patients with HIV infection have also been shown to experience periods of weight stability and weight gain.(41)