The aging process alone has no significant adverse consequences for the caloric intake and the nutritional status of healthy elderly individuals, Epidemiological data suggest that in humans, in contrast to rodents, undernutrition reduces the life span. In the Western World, malnutrition in old age has become uncommon and is, for the most part, the result of physical illness and/or of psychological and socioeconomic factors, such as depressive disorders, social isolation, smoking, alcohol abuse, and poverty. Body weight shows a U- or J-shaped relationship to mortality risk with the highest survival rates found at normal to moderate overweight. However, studies that have controlled for disease already present, smoking status, serum cholesterol level, or hypertension, suggest an increased mortality risk for lower and upper extremes of body weight, only. Populations with healthy lifestyles have significantly greater life expectancy than the average normal population. Even in the very old, exercise has been shown to improve muscle strength and function. The studies suggest that nutritional intake and nutritional status in old age is multifactorial and dependent not only on appetite and availability of diverse food, but also on physical activity, body mass, education, and an involved social lifestyle.
