Evidence for the anorexia of aging: gastrointestinal transit and hunger in healthy elderly vs. young adults

W. K. Clarkston, M. M. Pantano, J. E. Morley, M. Horowitz, J. M. Littlefield and F. R. Burton Department of Internal Medicine, Saint Louis University School of Medicine 63104, USA. Animal studies suggest that aging is associated with anorexia and disordered gastrointestinal transit. To determine whether there is a relationship between the effects of aging on appetite and gastrointestinal transit in humans, 19 young (age 23-50 yr) and 14 elderly (age 70-84 yr) normal volunteers underwent measurements of 1) desire to eat, hunger, and fullness (visual analog scales); 2) gastric emptying (scintigraphy); 3) orocecal transit (breath hydrogen); 4) total gut transit (radiopaque markers); and 5) autonomic nerve function (cardiovascular reflexes). We found that, postprandially, elderly subjects had less desire to eat (P < 0.05) and less hunger (P < 0.05), but not a significantly greater fullness than younger subjects. Gastric emptying (50% emptying time) for solid (182 +/- 26 vs. 127 +/- 13 min, P < 0.05) and liquid (47 +/- 4 vs. 35 +/- 3 min, P < 0.05) meal components was slower in elderly subjects. Postprandial hunger was inversely related (r = -0.39, P < 0.05) to solid gastric emptying. There were no significant differences in orocecal and total gut transit times between the two groups. Autonomic nerve function was abnormal in 11 elderly but none of the young subjects (P < 0.01). We conclude that aging is associated with 1) diminished desire to eat and hunger, 2) slowing of solid and liquid gastric emptying, 3 no change in orocecal and total gut transit, and 4) autonomic nerve dysfunction. The slowing of gastric emptying may contribute to anorexia in aging subjects.