Changes in food intake and its relationship to weight loss during advanced age.

The results of extensive human and animal studies suggest that declining food intake and body weight observed in the later stages of life may be part of the normal progression of physiological decline observed during aging. Proposed etiologies cover a wide range of biological and psychological conditions. Studies in humans suggest an imbalance in homeostatic mechanisms governing hunger and satiety. That is, while older vs. younger individuals retain a similar drive (hunger) to eat, satiety occurs sooner during a meal in aged people and leads to an overall decrease in daily food intake. Age-related weight loss and a reduction in food intake have also been observed in laboratory animals. Alterations in neurochemical control of energy balance, especially as they relate to long-term regulation of food intake, have received much attention in recent years as the likely mechanism underlying age-related spontaneous weight loss. Age-related changes to neuroendocrine factors such as neuropeptide Y, GABA, CCK, leptin, and insulin have been linked to spontaneous weight loss observed during late life. This brief review provides an update on putative mechanisms underlying the dysregulation of feeding during advanced age that result in body weight loss.