Exercise and BMI z-score in Overweight and Obese Children and Adolescents: A Systematic Review and Network Meta-Analysis of Randomized Trials

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Aim—Examine the effects of selected types of exercise (aerobic, strength training, both) on BMI z-score in overweight and obese children and adolescents. Methods—Randomized exercise intervention trials ≥ 4 weeks were included. Studies were retrieved by searching six electronic databases, cross-referencing and expert review. Dual selection and abstraction occurred. Risk of bias and confidence in cumulative evidence were assessed. Network meta-analysis was performed using multivariate random-effects meta-regression models while surface under the cumulative ranking curves were used to calculate a hierarchy of exercise treatments. The number needed to treat (NNT) and percentile improvement (U3) were also calculated. Results—Thirty-four studies representing 2,239 participants were included. Median exercise occurred 3 times per week, 50 minutes per session over a 12-week period. Statistically significant reductions in BMI z-score were found for aerobic exercise and combined aerobic and strength exercise, but not strength training alone (M±SD, 95% CI: aerobic, -0.10, -0.15 to -0.05; aerobic and strength, -0.11, -0.19, -0.03; strength, 0.04, -0.07 to 0.15). Combined aerobic and strength training was ranked best, followed by aerobic exercise and strength training. The NNT was 2 for both aerobic exercise and combined aerobic exercise and strength training. Percentile improvements were 28.8% for aerobic exercise and 31.5% for combined aerobic exercise and strength training. Confidence in effect estimates was ranked as low for aerobic exercise and very low for combined aerobic and strength training as well as strength training. Conclusions—Aerobic exercise and combined aerobic exercise and strength training are associated with reductions in BMI z-score.