Aging is associated with a reduction in appetite and food intake, predisposing to protein-energy malnutrition. The causes of this "anorexia of aging" are largely unknown. To investigate possible contributions of enhanced satiating effects of cholecystokinin (CCK) and reduced stimulation of food intake by ghrelin, eight undernourished older women [age, 80.4 +/- 2.6 yr; body mass index (BMI), 16.9 +/- 0.57 kg/m(2)], eight well-nourished older women (age, 77 +/- 0.9 yr; BMI, 23.7 +/- 0.8 kg/m(2)), and eight well-nourished young women (age, 22 +/- 1.3 yr; BMI, 20.5 +/- 0.4 kg/m(2)), in randomized order, ate on 1 d a 280-kCal preload and on the other no preload, 90 min before an ad libitum meal. At baseline the undernourished, but not the well-nourished, older subjects were less hungry (P < 0.05) than young subjects. Before and after the preload, plasma CCK levels were higher (P < 0.05) in the older than young subjects, with no difference between the older groups. Plasma ghrelin concentrations were higher in the undernourished than both well-nourished groups and decreased similarly after the preload in all groups. The preload suppressed food intake in the well-nourished older and young subjects (P < 0.05), but was without effect in the undernourished old. These observations suggest that reduced basal hunger, rather than increased meal-induced satiety, contributes to the anorexia of aging and that changes in CCK and ghrelin are unlikely to be responsible.