Percent body fat, but not lean mass, is associated with objectively measured physical function in middle-aged women

Abstract

ObjectivesThe relationship between components of body composition and physical function is not well characterized among middle-aged women. This cross-sectional study examined the strength of the associations between lean mass and percent fat and physical function in middle-aged women. Study DesignBody composition, physical function and physical activity were objectively measured in 80 women (mean age 52.58 ± 6.10 years; range = 40−63 years). Main Outcome MeasuresAdiposity (%Fat) and lean mass were measured via dual-energy x-ray absorptiometry. Steps/day and minutes of low-, moderate- and vigorous-intensity physical activity were assessed via accelerometer. Physical function was measured via a seated transfer task, 30-second chair stand, a six-minute walk task, 8-foot timed up and go, and a lift and carry task. Results: When controlling for steps/day, measures of lean mass were related to performance on the seated transfer task (r = .25) and 30-second chair stand (−.26) (both p > 0.05), while %Fat was related to performance on the seated transfer task (r = .53), 8-foot timed up and go (r = .32), 30-second chair stand (r = −.35), and six-minute walk (r = −.48; all p ≤ 0.05). Linear regression analyses revealed: (1) age, steps/day, and %Fat were independently related to performance on the seated transfer task and 30-second chair stand (both p ≤ 0.05), (2) %Fat was associated with six-minute walk and 8-foot up-and-go performance (p ≤ 0.01); none of the variables included were associated with lift and carry. ConclusionsAdiposity but not lean mass was associated with objectively measured physical function in middle-aged women. Interventions that focus on reducing body fat may be an effective method for improving functional performance among women in this age group.