Changes in Physical Activity and Body Composition in Postmenopausal Women over Time.

Publication Type:

Journal Article

Source:

Medicine and science in sports and exercise (2013)

Keywords:

2013, March 2013, Public Health Sciences Division

Abstract:

PURPOSE: Higher physical activity (PA) has been associated with greater attenuation of body-fat gain and preservation of lean mass across the lifespan. These analyses aimed to determine relationships of change in PA to changes in fat and lean body mass in a longitudinal prospective study of postmenopausal women. METHODS: Among 11,491 women enrolled at three Women's Health Initiative (WHI) clinical centers were selected to undergo dual-energy x-ray absorptiometry (DXA), 8,352 had baseline body composition measurements, with at least one repeated measure at yr 1, 3, and 6. PA data were obtained by self-report at baseline, 3 and 6 yr of follow-up. Time-varying PA impact on change in lean and fat mass during the six-yr study period for age groups (50-59y, 60-69y, 70- 79y) was estimated using mixed effects linear regression. RESULTS: Baseline PA and body composition differed significantly among the three age groups. The association of change in fat mass from baseline and time-varying PA differed across the three age groups (p=0.0006). In women aged 50-59, gain in fat mass from baseline was attenuated with higher levels of physical activity. Women aged 70-79 lost fat mass at all PA levels. In contrast, change in lean mass from baseline and time-varying PA did not differ by age group (p=0.1935). CONCLUSIONS: The association between PA and change in fat mass varies by age group, with younger, but not older, women benefitting from higher levels of aerobic PA. Higher levels of aerobic activity are not associated with changes in lean mass, which tends to decrease in older women regardless of activity level. Greater attention to resistance training exercises may be needed to prevent lean mass loss as women age.