Unbalanced serum leptin and ghrelin dynamics prolong postprandial satiety and inhibit hunger in healthy elderly: another reason for the 'anorexia of aging'

Background: In healthy elderly, a reduction from the appetite and food intake of younger years has been defined as the "anorexia of aging," which may cause malnutrition. Leptin and ghrelin may alter the control of hunger and satiety and thus lead to anorexia. Objective: The aim of this study was to investigate how aging affects serum leptin and ghrelin concentrations in response to a meal and the relation of those hormones to hunger and satiety sensations. Design: We studied 8 community-dwelling elderly (x! ! SD age: 78!1 y) subjects and 8 younger (29.5!1 y) control subjects. Under fasting conditions and for 4 h after an 800-kcal mixed meal, satiety and hunger were evaluated at intervals, by using a visual analogic scale. Blood samples for leptin, ghrelin, and insulin measurements were collected at the following times: 30 min before and immediately and 30, 60, 120, and 240 min after the meal. Results: Postprandial satiety lasted significantly longer in the elderly than in the control subjects, and hunger was suppressed in the elderly throughout the observation. Fasting leptin was higher in the elderly than in the young (x! ! SE: 4.3 ! 1.9 and 1.3 ! 0.4 ng/mL, respectively; P " 0.05), and postprandial fluctuation was not significant. Fasting insulin also was significantly higher in the elderly than in the young (6.8!1.3 and 3.5!0.6 mU/L, respectively; P" 0.05), and the postprandial insulin rise was greater in the elderly. Fasting and postprandial ghrelin values did not differ significantly between the 2 groups. Insulin was inversely correlated with hunger and directly correlated with satiety scores. Conclusions: In healthy elderly, anorexigenic signals prevail over orexigenic signals, and they contribute to prolonged satiety and inhibition of hunger. This condition may lead to a calorie deficit and finally to malnutrition in the elderly.