The relationship between cardiorespiratory fitness and indices of fat mass and fat-free mass in adults

Abstract

Purpose: Cardiorespiratory fitness (CRF) independently predicts cardiovascular disease risk and mortality. In addition, body composition levels characterized by excess adiposity (fat mass) and low levels of fat-free mass (FFM) are strongly associated with poor health status. The relationship between CRF and body composition, especially indices adjusted for height [fat mass index (FMI), fat-free mass index (FFMI)] has not been well established in otherwise healthy adults. Methods: A sample (n = 82) of adults completed measures for body composition using dual-energy x-ray absorptiometry and estimated V˙O2max by way of an Åstrand-Rhyming submaximal cycle ergometer test. Total daily energy expenditure (TDEE) and moderate-to-vigorous physical activity (MVPA) were measured using a SenseWear Armband activity monitor. The associations between body composition (FMI, FFMI), and CRF were examined using multiple linear regression models adjusting for sex (model 1) and TDEE (model 2). Results: Participants were young (age: 24 ± 9 year), 64% female, with a BMI of 25.4 ± 4.9 kg·m−2. The mean absolute and relative estimated V̇O2max were 3.02 ± 1.0 L·min−1 and 42.1 ± 12.2 ml·kg−1·min−1, respectively. FMI was negatively associated CRF (L·min−1) in model 2 (B = −0.106, 95%CI −0.16, −0.05, p < 0.001) but not model 1 (B = −0.011, 95%CI −0.03, 0.01, p = 0.271). FFMI was positively associated with CRF (L·min−1) (model 1: B = 0.087, 95%CI 0.03, 0.14), p = 0.004) but not after adjusting for TDEE (model 2: B = 0.026, 95%CI −0.07, 0.12, p = 0.585). Conclusion: FM adjusted for height (FMI), but not fat-free mass (FFMI), is negatively associated with cardiorespiratory fitness in adults.