Impaired regulation of energy intake in old age.

Abstract

Aging is associated with predictable alterations in body fat that are thought to have an important impact on health. From early adult life through middle age there is a substantial increase in body fat [1, 2], while after 65–70 years of age body fat typically decreases, even in healthy individuals [1, 2]. Unexplained weight loss becomes relatively common after the age of 65 [3, 4] and 30–50% of institutionalized elderly are reported to suffer from proteinenergy malnutrition [3, 4]. This loss of body fat in later years is associated with several adverse factors including micronutrient deficiencies, frailty, increased hospital admission, an increased risk of disability from falls, delayed recovery from injury and premature death [5–8]. As reviewed elsewhere [9–12], negative energy balance resulting from low energy intake relative to total energy expenditure is suggested to be the usual cause of the loss of body fat in old age and, consistent with this suggestion, nationwide studies have suggested that low dietary energy intake is widespread even among healthy elderly adults [13]. However, the underlying determinants of low energy intake remain uncertain. There are several factors, such as reductions in the sensations of taste and smell, poor dentition, prescription medications, depression and social isolation that may possibly promote inadequate energy intake [14–17]. In addition, an impairment in the ability to regulate food intake, termed the ‘anorexia of aging’ [15], is speculated to be important. This chapter synthesizes recent results and reviews [9–12] on changes in the regulation of food intake in old age and the possible underlying mechanisms.