Independent and joint associations of out-of-school time moderate-to-vigorous physical activity and sedentary behavior with the risk of central obesity in children and adolescents

Physical activity (PA) and sedentary behavior (SED) are closely associated with central obesity in children and adolescents. However, the relationships between out-of-school time PA, SED, and central obesity remain insufficiently explored. This study aimed to examine the independent and joint associations of out-of-school time moderate-to-vigorous physical activity (MVPA) and SED with the risk of central obesity in children and adolescents. This study used cross-sectional data from the China Health and Nutrition Survey (CHNS) covering the period from 2004 to 2015. Multivariate logistic regression was employed to analyze the independent and joint associations between out-of-school MVPA, SED, and central obesity risk. Restricted cubic spline (RCS) was used to assess the corresponding nonlinear associations. This study included 4460 participants with a median age of 11 years, of whom 23.6% had central obesity. In models including both MVPA and SED, medium (OR = 0.78, 95% CI: 0.66, 0.93) and high MVPA groups (OR = 0.81, 95% CI: 0.68, 0.97) were associated with lower central obesity risk compared with the low MVPA group. The high SED group was associated with a higher central obesity risk compared with the low SED group (OR = 1.26, 95% CI: 1.06, 1.50). Additionally, a nonlinear dose-response relationship was observed between out-of-school MVPA and central obesity risk (P – nonlinear = 0.021). The joint association of low SED and high MVPA was associated with the lowest risk (44% lower) for central obesity. However, compared to the combination of high SED and low MVPA, neither the high SED and high MVPA group (OR = 0.84, 95% CI: 0.63, 1.11) nor the low SED and low MVPA group (OR = 0.78, 95% CI: 0.60, 1.03) was associated with a lower risk of central obesity. This study suggests that higher MVPA and lower SED during out-of-school periods are associated with lower central obesity risk in children and adolescents. Engaging in 30–60 min of out-of-school MVPA per day was associated with the lowest risk of central obesity. For high-SED youth, engaging in medium (rather than high) out-of-school MVPA is associated with lower central obesity risk. In contrast, low-SED individuals need to engage in at least medium levels of out-of-school MVPA to demonstrate an association with lower central obesity risk.