Energy expenditure in Alzheimer's disease

Alzheimer's disease type dementia is a growing health problem and is one of the leading causes of death among elderly people. Unexplained weight loss and cachexia is a frequent clinical finding in patients with Alzheimer's disease. It has been postulated that Alzheimer's disease may by characterized by dysfunction in body weight regulation. This brief review examines energy intake, energy expenditure and body composition in Alzheimer's disease. We consider whether inappropriately high levels of energy expenditure may contribute to unexplained weight loss and decline in nutritional status. Specifically, we will consider studies that have examined body composition, daily energy expenditure and its components. The application of doubly labeled water and indirect calorimetry to problems of "wasting" has increased our knowledge regarding energy expenditure and physical activity levels in Alzheimer's patients. Although the number of studies are limited, results do not support the notion that a "hypermetabolic" state contributes to unexplained weight loss in Alzheimer's disease, even in cachectic patients. Clinical strategies aimed at developing feeding strategies to maintain adequate caloric intake and the restoration of energy balance should be a future area of investigation in Alzheimer's research.