Children’s body mass index may affect physical activity (PA) participation. Therefore, this study examined the effect of children’s weight status on underserved elementary school children’s PA and sedentary behavior (SB) throughout the segmented day. Participants were 138 children ($\overline{\mathrm{X}}$age = 8.14 years). Children’s height and weight were measured with subsequent classification of children as healthy weight or overweight/obese. Durations of moderate-to-vigorous PA (MVPA), light PA (LPA), and SB during physical education (PE), morning recess, lunch recess, after school, and overall were assessed via accelerometry over three days. Independent t-tests evaluated differences in children’s MVPA, LPA, and SB during each daily segment by weight status. Significantly higher MVPA was observed for children of healthy weight status versus children with overweight/obesity during morning recess, t(136) = 2.15, p = 0.03, after school, t(136) = 2.68, p < 0.01, and overall, t(136) = 2.65, p < 0.01. Interestingly, comparisons of children of healthy weight status and children with overweight/obesity’s LPA and SB during the after-school segment revealed a trend wherein children with overweight/obesity participated in slightly greater LPA/less SB than children of healthy weight status. Higher MVPA was observed among children of healthy weight versus children with overweight/obesity during most daily segments. Concerted efforts should focus on increasing MVPA among children with overweight/obesity.

Depression has become the most prevalent mental health problem in developing countries, and especially among adolescents. Lubans and his colleagues proposed a psychosocial mechanism to understand the trajectory of mental health (i.e., depression). Thus, this study aimed (1) to examine the relations between different doses of physical activity (PA), light PA (LPA), moderate PA (MPA), and vigorous PA (VPA), academic self-efficacy, and depression among adolescents, and (2) to investigate the direct and indirect relations of various doses of PA to depression through academic self-efficacy among middle school adolescents. Participants were 428 (235 boys, Mean _age = 13.7) adolescents recruited from two middle schools in China. They completed previously validated questionnaires to measure different intensity levels of PA (LPA, MPA, and VPA), academic self-efficacy, and depression. There were significant associations of academic self-efficacy with three different doses of PA (p < 0.01). Both LPA and MPA were negatively associated with depression but not VPA. Structural equation modeling (SEM) revealed a well-fit model suggesting the psychosocial pathway from different doses of PA to depression through academic self-efficacy. Findings of this study indicated that academic self-efficacy regulates adolescents’ depression. Tailoring different intensities of PA benefits adolescents’ academic self-efficacy by framing the positive and supportive environment in schools, which can potentially reduce the prevalence of depression during adolescence.