Physical activity in relation to body size and composition in women in UK Biobank

Purpose: Physical activity is thought to protect against obesity, but the evidence is limited and few large studies of this topic have direct, objective measures of several different anthropometric variables. We examined the association of self-reported physical activity with measures of total and central adiposity.

Methods: Our cross-sectional study included 38,201 premenopausal and 94,592 postmenopausal healthy women aged 40 to 70 years in UK Biobank, recruited from 2006 to 2010.

Results: Means for total and vigorous physical activity were 31.3 (SD, 30.8) and 9.7 (SD, 14.8) metabolic equivalent h/wk, respectively, for premenopausal and 34.4 (SD, 33.1) and 8.9 (SD, 15.6) metabolic equivalent h/wk, respectively, for postmenopausal women. Multiple linear regression models showed that in both premenopausal and postmenopausal women, body mass index, body fat mass and percentage, trunk fat mass and percentage, waist and hip circumference, and waist-to-hip ratio were lower in women with higher physical activity (P < .0001). Within each category of total physical activity, a larger proportion of vigorous physical activity was associated with lower adiposity (P < .0001).

Conclusions: These findings support the roles of a physically active lifestyle and vigorous exercise in maintaining healthy body size and composition. Higher exercise intensity may be associated with lower adiposity, beyond the influence of exercise frequency and duration.