CONTROL OF FOOD-INTAKE IN OLDER MEN

Objective.-To investigate the effects of aging on mechanisms of body e nergy regulation and thereby determine the causes of unexplained weigh t loss in older persons, a factor predisposing to premature death and disability. Design.-Dietary intervention study. Setting.-Metabolic war d and outpatient. Participants.-The subjects were 35 healthy younger a nd older men of normal body weight consuming a diet of typical composi tion and performing usual activities. Main Outcome Measures.-Subjects were either overfed by a mean (+/-SD) of 4.09 (+/-0.26) MJ/d (n=17) or underfed by 3.17 (+/-0.68) MJ/d (n=18) for 21 days. Measurements were made of changes in body weight, body composition, and energy expendit ure during overfeeding or underfeeding, and of subsequent voluntary nu trient intakes and changes in body weight. Results.-There was no signi ficant effect of aging on changes in body composition, body weight, or energy expenditure with overfeeding or underfeeding. However, followi ng overfeeding, younger men exhibited spontaneous hypophagia, whereas the older men did not (mean [+/-SD] changes in energy intake relative to control values were -2.11 [+/-2.18] and 1.55 [+/-2.11] MJ/d, respec tively; P=.006). As a result, the younger men lost the excess body wei ght gained during overfeeding but the older men did not. Similarly, fo llowing underfeeding, the younger men exhibited hyperphagia while the older men did not (mean [+/-SD] changes in energy intake relative to c ontrol values were 1.88 [+/-2.31] and -0.52 [+/-1.54] MJ/d, respective ly; P=.02), and as a result the older men failed to regain the weight lost during underfeeding. Conclusions.-These results in 35 men suggest that aging may be associated with a significant impairment in the abi lity to control food intake following overeating or undereating. Since overeating and undereating occur routinely as part of the normal patt ern of energy regulation, the findings reported herein may help to exp lain the vulnerability of older persons to unexplained weight gain and weight loss.