Invited Review: Aging and energy balance

Abstract

Humans over 70 yr of age often lose weight. This appears to be due to a physiological anorexia of aging as well as a loss of lean mass (sarcopenia) and, to a lesser extent, fat mass. The causes of the physiological anorexia of aging include changes in taste and smell and a decrease in adaptive relaxation of the fundus of the stomach, which leads to more rapid antral filling and early satiation. In addition, basal and stimulated levels of the satiating hormone, cholecystokinin, are increased. In men, the decline in testosterone leads to an increase in leptin and a loss of lean mass. Although resting metabolic rate declines with aging, this is mainly due to the decline in lean body mass. Energy metabolism is also decreased due to a decline in Na+-K+-ATPase activity, decreased muscle protein turnover, and possibly changes in mitochondrial membrane protein permeability. Physical energy expenditure declines with aging. Meal-induced thermogenesis shows a delay to peak, possibly due to a delay in gastric emptying. Inadequate data are available on the effect of aging in humans on other energy-producing mechanisms such as adaptive thermogenesis. These physiological changes place older men and women at major risk of developing pathological weight loss when they develop disease states, especially those associated with cytokine elaboration.

Age-Dependent Brain Tissue Hydration, Ca Exchange and their Dose- Dependent Ouabain Sensitivity

“…It is widely recognized that although neural cell swelling can be observed under physiological conditions, for example as a result of neurotransmission or intense neuronal discharge (4,(43)(44)(45), larger changes are encountered during pathological conditions, including aging. It is known also that neuronal dehydration in older adults is a reliable predictor of increasing frailty, progressive deterioration in cognitive function and an overall reduction in quality of life [46][47][48][49]. There are a number of hypotheses on regard of detailed role of agedependent cell dehydration in deterioration in cognitive function of brain.…”

Odour and taste sensitivity is associated with body weight and extent of misreporting of body weight

“…After the sixth decade, a moderate weight loss is observed through to the ninth decade of life (Roubenoff, 2000;Wilson and Morley, 2003;Janssen et al, 2004;Roubenoff, 2004). Although this reduction of body weight is generally observed and independent of any disease process (Roubenoff, 2004), it may also be inversely related to general well-being.…”

Disorders of appetite and eating

“…The anorexia is partly due to changes in taste and smell. Adaptive relaxation of the fundus of the stomach is also reduced, leading to more rapid filling and early satiety [7]. In addition, the level of the satiating hormone CCK increases with age [1].…”

“…In addition, the level of the satiating hormone CCK increases with age [1]. Nutritional interventions may be beneficial in preventing weight loss but maintenance of physical activity too is essential for a good outcome [7].…”