Aging, body composition, and lifestyle: the Fels Longitudinal Study

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Abstract
Background: Changes in body composition in men and women occur with age, but these changes are affected by numerous covariate factors. Objective: The study examined patterns of change in body composition and determined the effects of long-term patterns of change in physical activity in older men and women and in menopausal status and estrogen use in women. Design: Serial measures of height, weight, body mass index (BMI), total body fat (BF), percentage BF, and fat-free mass (FFM) from underwater weighing of 102 men and 108 women enrolled in the Fels Longitudinal Study were analyzed. Physical activity levels and menopausal status were included as covariates. Results: There were significant age-related decreases in FFM and height and increases in total BF, percentage BF, weight, and BMI. Physical activity was associated with decreases in total BF, percentage BF, weight, and BMI in men and were associated with increases in FFM and decreases in total BF and percentage BF in women. Postmenopausal women had significantly higher total BF and percentage BF than did pre- and perimenopausal women. The longer the time since menopause the greater were the increases in weight, BMI, total BF, and percentage BF; however, estrogen use attenuated these increases. Conclusions: Low FFM can be improved by increased physical activity. The effects of an intervention program on body composition can be masked if only body weight or BMI is measured. The effects of physical activity were more profound in postmenopausal than in premenopausal women, and estrogen use had beneficial effects on body composition.