Despite tremendous advances in treatment, persons with human immunodeficiency virus (HIV) infection commonly experience a variety of nutritional problems, such as weight loss, fat redistribution, and obesity. We discuss basic dietary and metabolic problems as they pertain to persons with HIV infection and provide practical suggestions for their management. In all persons, changes in weight are caused by disruptions of energy balance, which can be disturbed by alterations in energy intake (effective ingestion of calories), energy expenditure (use of calories), or both. Factors that contribute to the disturbance of energy balance are discussed in the context of HIV infection. Management of weight loss and weight gain may then be directed at the affected components of energy balance. This information is intended to raise health care providers' attention to nutrition in their patients, including monitoring of weight, dietary issues, and relevant symptoms, and to encourage liaisons with experienced dietitians and exercise trainers.