The “Fat or Fit Paradox” in Postmenopausal Women: A Cross-Sectional Study on the Association Between Skeletal Muscle Mass, Adiposity, and Muscle Strength

Abstract

Background. The “Fat or Fit Paradox” denotes an intriguing association between muscle mass and adiposity in older individuals, challenging conventional beliefs on health and fitness. This investigation seeks to elucidate this paradoxical relationship in a cohort of postmenopausal women. Methods. In a cross-sectional study, we assessed the correlation between skeletal muscle mass and body fat percentage in 134 community-dwelling Malaysian post-menopausal women, aged 45-88 years. Body composition parameters, including skeletal muscle mass and fat indices, were measured utilizing a multi-segmental bioelectrical impedance analyzer (InBody 230), while muscle strength was indirectly determined by handgrip strength assessment using a JAMAR HAND dynamometer. Results. Our analysis revealed a significant positive correlation between appendicular skeletal muscle mass index (ASMI) and body fat percentage (r = 0.359, p < 0.001), indicating that increased adiposity is linked to higher muscle mass in older women. Linear regression analyses further demonstrated a significant positive association between muscle strength and ASMI (R2 = 0.195, p < 0.001). Importantly, upon stratification by obesity status, muscle mass emerged as a significant predictor of muscle strength in low-obese participants; however, the predictive power decreased with escalating obesity levels. Conclusions. Our findings confirm a positive association between skeletal muscle mass and body fat percentage in postmenopausal women, although muscle strength exhibits caveats contingent on obesity status. This study accentuates the importance of appraising both muscle mass and adiposity when evaluating overall health and fitness in an aging population.