UC Irvine

Background and Objective Postmenopausal women tend to experience significant changes in body composition, particularly abdominal adipose tissue (AAT) deposition patterns, which are hypothesized to be critical factors influencing future cardiometabolic disease risk. Physical activity has a demonstrable effect on body composition and overall health. However, there is little evidence for how different intensities and durations of physical activity over a sustained period of time influence AAT patterns and other measures of body composition in postmenopausal women. We emulated a target trial of physical activity interventions, including the 2018 Physical Activity Guidelines for Americans recommendations, on 3-year changes in AAT and body composition. Methods We analyzed observational data from 4,451 postmenopausal women aged 50-79 years in the Women's Health Initiative (WHI) to emulate a three-year target trial of adhering to increasing minutes of moderate (at least 15, 30, 75, 150, 300 minutes/week) and vigorous (at least 15, 30, 75, 150 minutes/week) physical activity aligned with the physical activity guidelines. All participants had repeated whole body Dual X-Ray Absorptiometry (DXA) scans with derived abdominal visceral (VAT) and subcutaneous adipose tissue (SAT). The measured differences in average levels of VAT, SAT, and other body composition measures determined at end of follow-up were estimated with the parametric-g formula. Results Over 3 years, interventions of increasing minutes of moderate activity would result in dose-dependent reductions in abdominal VAT, SAT, and overall body fat, and increases in lean soft tissue, with the greatest estimated benefit at the 2018 physical activity guideline recommendation of 150 mins/wk or more. Compared to no intervention, if all participants had adhered to at least 150 mins/wk of moderate physical activity, they would have 16.8 cm2 lower VAT (95% CI -23.1, -10.4), 26.8 cm2 lower SAT (95% CI -36.3, -17.3), 1.3% lower total body fat% (95% CI -1.8, -0.7), 1.2 % higher total lean soft tissue% (95% CI 0.7, 1.8), and 2.6 kg lower total bodyweight (95% CI -3.6, -1.5). We saw similar patterns in our vigorous-intensity activity interventions - if all participants adhered to at least 150 mins/wk, they would have experienced 6.7 cm2 lower VAT (95% CI -17.7, 4.3), 13.3 cm2 lower SAT (95% CI -28.8, 2.1), 1.0 % lower total body fat percent (95% CI -2.0, 0.0 ), % higher total lean soft tissue percent (95% CI) and a 0.9 kg lower total bodyweight (95% CI -2.7, 0.8). Conclusion This hypothetical emulated intervention indicated that postmenopausal women who adhere to physical activity guideline recommendations would experience beneficial changes in abdominal VAT, SAT, and overall body composition over 3 years. The study results underscore the imperative to explore further how physical activity may serve as a potential determinant of body composition.