Weight loss is a common problem in HIV infection, especially in the more advanced stages of AIDS. Weight loss of greater than 40% of lean body mass is an independent predictor of mortality. Weight loss of greater than 10% of body weight with no obvious underlying opportunistic infection or neoplasm has been termed the HIV wasting syndrome and is an AIDS-defining illness. The cause of weight loss in HIV-infected patients is multifactorial and includes diminished intake, malabsorption and increased metabolic rate. The major cause for weight loss in most patients has been shown to be inadequate caloric intake. Anorexia is a common result of systemic infection and drug side effects. Patients with oropharyngeal and esophageal pathology have discomfort related to eating and will decrease intake. The presence of gastrointestinal involvement is often associated with variable degrees of malabsorption so that the limited calories that are taken in are not assimilated efficiently. Increased basal metabolic rate as well as inefficient use of energy has been demonstrated in some cases. All of these contribute to weight loss.

There is no reliably effective treatment for wasting. Underlying opportunistic infections should be treated if possible. Caloric intake should be optimized; assistance of a dietitian is invaluable in helping patients maximize caloric intake. Intervention with enteral or parenteral nutritional support has not been shown to be generally effective, but may be used successfully in selected cases. Appetite stimulants such as megestrol acetate have been shown to be effective, producing weight gain in patients with anorexia and limited intake. The weight gained appears to be predominantly fat, and whether this translates into an improved survival rate or quality of life has not been established. Metabolic agents such as anabolic steroids and growth hormone have been used with limited success but are not currently in widespread use.