Effect of aging on the response of ghrelin to acute weight loss

OBJECTIVES: To determine whether the failure of the orexigenic hormone ghrelin to increase as it normally does with weight loss contributes to impaired weight recovery in older persons. DESIGN: Prospective diet intervention study. SETTING: University of Washington Medical Center from 2001 through 2005. PARTICIPANTS: Twenty-one younger (18-35) and 18 older (>= 70) men and women. INTERVENTION: Two weeks of a weight-maintaining diet were followed in sequence by 2 weeks of 30% calorie restriction, then 4 weeks of ad libitum food intake. MEASUREMENTS: Twenty-four-hour plasma ghrelin levels, dual x-ray absorptiometry scan for body composition, resting energy expenditure, and calorie intakes were measured. RESULTS: Both younger and older subjects lost weight with calorie restriction and failed to fully regain their baseline weight. The older adults trended toward increasing their calorie intake above their baseline level during the ad libitum period (111 +/- 66 kcal, P=.11), whereas the younger individuals did not (-236 +/- 95 kcal, P=.02). There was no statistically significant difference between the two cohorts in 24-hour ghrelin levels before or after calorie restriction. Ghrelin levels in the two cohorts increased equivalently after calorie restriction and decreased after ad libitum food consumption resumed. CONCLUSION: Ghrelin levels in healthy older individuals respond appropriately in a compensatory manner to changes in body weight and calorie intake.