The energetics of wasting diseases.

PURPOSE OF REVIEW: Unintentional weight loss or wasting continues to be a nutritional problem in the treatment of HIV/AIDS, cancer and many other diseases. Although wasting is a general sign of energy imbalance, the relative contribution of increased energy demands and decreased energy intake remains incompletely understood.

RECENT FINDINGS: Until the development of the method using doubly labeled water for measuring total energy expenditure, it was difficult to obtain unbiased estimates of total energy expenditure, particularly in clinical populations. Although costly, this technique provides greater insight in the energy requirements of clinical populations and the relative contributions of energy expenditure, energy intake and disease to wasting diseases. Although data are available in only a small portion of wasting diseases, the data suggest that even in the presence of increased demands for resting metabolic rate, total energy expenditure is often reduced because of decreased physical activity.

SUMMARY: Wasting is often the result of endocrine disorders accompanying the disease process itself. This, coupled with reduced energy intake, is often the primary contributor to wasting.