Physical activity and body mass: changes in younger versus older postmenopausal women.

PURPOSE: The study's purpose was to investigate the relationship of sedentary (≤ 100 MET · min · wk(-1)), low (>100-500 MET · min · wk(-1)), moderate (>500-1200 MET · min · wk(-1)), and high (>1200 MET · min · wk(-1)) habitual physical activity with body weight, body mass index, and measures of fat distribution (waist-to-hip ratio) in postmenopausal women by age decades.
METHODS: A prospective cohort study of 58,610 postmenopausal women age 50-79 yr weighed annually during 8 yr at one of 40 US clinical centers was analyzed to determine the relationship of high versus low habitual physical activity with changes in body weight and fat distribution by age group.
RESULTS: Among women age 50-59 yr, there was significant weight loss in those expending >500-1200 MET · min · wk(-1) (coefficient = -0.30, 95% confidence interval = -0.53 to -0.07) compared with the group expending ≤ 100 MET · min · wk(-1). Among women age 70-79 yr, higher physical activity was associated with less weight loss (coefficient = 0.34, 95% confidence interval = 0.04-0.63). Age at baseline significantly modified the association between physical activity and total weight change, whereas baseline body mass index did not.
CONCLUSIONS: High habitual physical activity is associated with less weight gain in younger postmenopausal women and less weight loss in older postmenopausal women. These findings suggest that promoting physical activity among postmenopausal women may be important for managing body weight changes that accompany aging.