Relevance of Physical Activities, Sedentary Behaviors, and Genetic Predisposition in Body Fatness: Population-Based Study on Chinese Adults

Introduction: Little attention has been paid to the interacting effect of specific intensities of physical activities (PAs) and sedentary lifestyle, like television watching, and genetic predisposition on body composition indices among Chinese adults. Herein, we aimed to examine whether specific types of PAs and sedentary behaviors (SBs) were associated with body composition indices among Chinese adults and to further explore whether these associations interacted with the genetic predisposition to high BMI. Methods: Cross-sectional data regarding PAs and time spent on SBs and dietary intake of 3,976 Chinese adults (54.9% women) aged 25–65 years in Southwest China were obtained via questionnaires in 2013–2015. Weight, height, and waist circumference (WC) were measured, and BMI, percentage of body fat (%BF), fat mass index (FMI), and fat-free mass index (FFMI) of the participants were calculated. Genetic risk score (GRS) was calculated on 9 established BMI-associated SNPs among Chinese adults. Results: When the participants were stratified by GRS for BMI, significant associations were only found for adults with high GRS for BMI: moderate-to-vigorous physical activity (MVPA) was negatively associated with WC and %BF and positively related to FFMI. The adjusted positive relationship of time spent watching television with BMI, WC, %BF, and FMI were also just found between adults with high weighted GRS for high BMI: for every 1 h increment in television watching, the BMI, WC, %BF, and FMI of the participants increased by 0.2 kg/m2, 0.9 cm, 0.3%, and 0.1 kg/m2, respectively (p < 0.02). Conclusion: MVPA may be a protective factor against obesity, and prolonged television watching may accentuate adiposity. These putative effects may be more pronounced among individuals with a high genetic risk of a high BMI.