Factors influencing body fat percentage at Q1.

With rising incomes in developing countries, the required necessary physical activity declines and the availability of snacks increases, further causing obesity in adolescents. The study was a longitudinal two-stage observational study of 74 overweight and obesity adolescents distinguishing between school and home environment phases. Data were collected at three time points (mid-semester (T0), end of semester (T1), and end of the winter holidays (T2)), and explorations were conducted using multivariate linear regression and Granger causality tests to investigate how changes in moderate-to-vigorous physical activity(MVPA), snacking habits (proportion of snack calorie, PSC; proportion of snack calories from protein, PSCP) in multiple stages and how their changes affect body composition. The results showed that during the semester phase, increases in ΔMVPA and ΔPSCP and decreases in ΔPSC were associated with decreases in ΔBFP (Δ = post-timepoint value − pre-timepoint value). During the holiday phase, decreases in ΔPSCP, MVPA (T1), and PSCP (T1), and increases in ΔPSC were associated with increases in ΔBFP. Only MVPA having a positive predictive effect causally on FFM. Snacking habits have a significant impact on body composition changes in adolescents, and reducing snack intake and choosing high-protein snacks are critical to controlling obesity in adolescents, especially during the holiday period. Strategies to increase MVPA should also be implemented to increase FFM briefly indirectly control obesity.

随着发展中国家居民收入水平提升，青少年日常所需体力活动量下降，且零食可获得性提升，进而进一步引发青少年肥胖问题。本研究为一项纵向两阶段观察性研究，纳入74名超重及肥胖青少年，区分校园环境与家庭环境两个阶段开展研究。研究于三个时间节点采集数据：学期中（T0）、学期末（T1）及寒假结束时（T2）；采用多元线性回归与格兰杰因果检验展开分析，探究多阶段中高强度体力活动（moderate-to-vigorous physical activity, MVPA）、零食摄入习惯[零食热量占比（proportion of snack calorie, PSC）、零食热量中蛋白质占比（proportion of snack calories from protein, PSCP）]的变化情况，及其变化对身体成分的影响。研究结果显示，在校学期阶段，中高强度体力活动变化量（ΔMVPA）与零食热量中蛋白质占比变化量（ΔPSCP）的提升，以及零食热量占比变化量（ΔPSC）的下降，与体脂百分比变化量（ΔBFP，Δ=后测时间点值-前测时间点值）的降低呈相关关系。假期阶段，ΔPSCP、T1节点MVPA及T1节点PSCP的下降，与ΔPSC的提升均与ΔBFP的升高呈相关关系。仅MVPA对去脂体重（Fat-Free Mass, FFM）具有显著的因果预测效应。零食摄入习惯对青少年身体成分变化具有显著影响，减少零食摄入量并选择高蛋白零食，是管控青少年肥胖的关键举措，尤其在假期阶段。此外，还应推行提升MVPA的相关策略，以增加去脂体重，进而间接实现肥胖管控的目标。