BackgroundPhysical activity (PA) intervention is a commonly recommended strategy to combat childhood obesity. However, its effectiveness has long been controversial. This paper aims to examine the effectiveness of long-term (≥12 months) school-based PA interventions on body mass index (BMI) in primary school children, who are gaining BMI.MethodsOriginal papers were retrieved from PubMed, Google Scholar, the Cochrane Library and Web of Science, published between 1990 and 2015. The inclusion criteria were those research studies that were: randomized controlled trials (RCTs), conducted in primary school settings, had valid data on BMI at baseline and at the final follow up (or on BMI changes), and involved PA intervention that lasted for at least 12 months.ResultsOut of 11,158 potentially eligible articles, 18 papers were included in the analysis, involving 22,381 primary school children with intervention durations ranging from 12 to 72 months. Compared to the control groups, the BMI increment was 2.23 kg/m2 less in the intervention groups (p < 0.05). The heterogeneity was high across the studies (99.8 %), but declined after sub-group analyses. The intervention type, intervention duration, and weekly PA intervention time were among the factors leading to the heterogeneity.ConclusionLong-term school-based interventions containing PA as a core component appear to be effective in achieving healthier BMI. However, the results should be interpreted with caution due to the high heterogeneity among the studies. More high quality school-based RCTs among diverse populations are needed to improve the homogeneity and to yield a more robust conclusion.

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To investigate the effects of maternal fasting plasma glucose (FPG) and pre-pregnancy weight status (PPWS) on offspring birth measures and body mass index z-score (BMI-z) in the first year, we conducted a prospective study of 1,096 mother-infant dyads in Guangdong, China, 2014–2015. Multivariate logistic regression was used to test independent/interaction associations of maternal FPG and PPWS with macrosomia/large for gestational age (LGA). Association of PPWS and FPG with offspring BMI-z in the first year was assessed by the linear mixed effects models. For each 1-mmol/L increase in FPG, the risk of macrosomia and LGA was elevated by 2.74 and 2.01 (95% CI: 1.85, 7.60 and 1.54, 5.88), respectively. No main effect of PPWS or interaction association of FPG and PPWS on macrosomia/LGA was observed (P > 0.05). A relation between maternal FPG and PPWS was detected (P < 0.05). Infants of Q5 FPG mothers, those who were born to OWO mothers, had a 0.35 increase in the BMI-z (95% CI: 0.16, 0.55) compared with infants of NW mothers. In conclusion, maternal FPG is positively associated with macrosomia/LGA. Maternal PPWS and FPG considerably interacted for the association with the risk of offspring high BMI-z in the first year.

We aimed to assess whether hypertensive disorders of pregnancy (HDP) could modify the effect of pre-pregnancy overweight or obesity (OWO) on the risk of offspring high body mass index (BMI) in infancy. A total of 3,765 mother-child pairs were recruited from two Chinese birth cohorts. BMI ≥ 85th percentile, based on World Health Organization criteria, was defined as a high BMI for the risk of developing severe obesity in later life. Logistic regression analysis was used to assess the combined effects and multiplicative interactions of pre-pregnancy OWO + HDP on offspring high BMI. Relative excess risk due to interaction (RERI) or attributable proportion (AP) was used to estimate additive interactions. RERI > 0 or AP > 0 indicates a significant additive interaction. Compared with the non-OWO and normal blood pressure group, the combination of OWO + HDP was positively associated with offspring high BMI at 12 months of age [OR 3.10 (95%CI 1.59, 6.04)], with 51% of the effects attributed to an additive interaction [AP 0.51 (95%CI 0.13, 0.89)]. An interactive effect was found between the pre-pregnancy OWO + HDP and offspring high BMI in infancy. Interventions to control pre-pregnancy OWO and HDP are important to prevent obesity and associated adverse outcomes in offspring.