NGHC: Prevention of Chronic Disease (2013)

Study Design:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
To determine the effect of school-based physical activity interventions on body mass index (BMI) in children.
Inclusion Criteria:
  • Randomized and non-randomized controlled trials with appropriate control groups
  • School-based exercise or physical activity intervention
  • Control group could not receive intervention
  • School age (five to 18 years)
  • Objective height and weight data
  • Minimum study duration of six months
  • If study results are published in more than one article, BMI data were included only once
  • No language restriction
  • For meta-analysis: Complete BMI data.
Exclusion Criteria:
  • Not meeting inclusion criteria
  • For meta-analysis: Incomplete BMI data. 
Description of Study Protocol:


  • Four electronic databases searched:
    • MEDLINE (January 1966 to September 2008)
    • Cochrane CENTRAL Register of Controlled Trials (up to September 2008)
    • EMBASE (January 1980 to September 2008)
    • CINAHL (January 1982 to September 2008)
  • Hand-searched the electronic versions of the following journals from January 2003 through September 2008:
    • Pediatrics
    • Journal of Pediatrics
    • Archives of Pediatric and Adolescent Medicine
  • Authors searched the reference lists of included articles and relevant reviews for additional studies
  • The following MeSH terms were searched: “Obesity” or “overweight” and “schools” and “child” or “adolescent” and “exercise.”


Systematic review with meta-analysis on subgroup of studies.

Statistical Analysis

  • Heterogeneity of summary estimates was assessed using the I2 statistic
  • Publication bias was assessed using a funnel plot
  • Multiple one-way sensitivity analyses were completed to assess the robustness of the results
  • Additionally, results were compared for:
    • Studies with and without co-interventions
    • Studies longer and shorter than one year
    • Studies with both girls and boys vs. those with only one sex
    • Randomized controlled trials vs. controlled clinical trials.
Data Collection Summary:

Timing of Measurements

Included studies were published between 1996 and 2007.

Dependent Variables

BMI change.

Independent Variables

School-based physical activity intervention.

Control Variables

  • Sex of subjects
  • Design of trial
  • Duration of intervention
  • Presence of co-interventions
  • Quality of intervention (measured using Jadad criteria and the Cochrane Effective Practice and Organization of Care Review Group criteria).
Description of Actual Data Sample:
  • Initial N: 398 studies initially identified
  • Attrition (final N): 18 unique studies included in the systematic review, 15 studies used in the meta-analysis. The sample of studies comprised analysis on 18,141 children.
  • Age: Five to 18 years
  • Ethnicity: Summary characteristics not reported.

Other Relevant Study Characteristics

  • 15 studies included some measure of physical activity
  • No studies objectively measured adherence to program at individual level
  • Three studies included only physical activity intervention and 15 studies included co-intervention (e.g., classroom nutrition education, health education or family involvement)
  • Study duration ranged from six months to three years (median 18.5 months).


  • US: 12 studies
  • Canada: Three studies
  • Australia, Chile, Sweden: One study.
Summary of Results:

Primary Outcome

  • The change in BMI was not statistically significant between children who received school-based physical activity interventions and those who did not (weighted mean difference was -0.05kg/m2; 95% CI: -0.19 to 0.10)
  • The result was statistically heterogeneous. There was no indication of publication bias.

Sensitivity Analysis

  • When only RCTs were included in the meta-analysis, difference in BMI change was still not significant (though the results were no longer statistically heterogeneous)
  • The presence of co-interventions did not affect the results
  • The duration of the study did not affect the results
  • Study quality did not affect the results
  • Sex of students did not affect the results.
Author Conclusion:
  • Body composition did not improve with participation in a school-based physical activity program
  • Nonetheless, it is still important to promote school-based physical activity programs because studies have demonstrated significant benefits in other areas (e.g., increasing lean muscle mass, bone density and aerobic capacity as well as improving flexibility).
Funding Source:
Other: none reported
Reviewer Comments:


  • sensitivity analysis
  • meta-analysis
Quality Criteria Checklist: Review Articles
Relevance Questions
  1. Will the answer if true, have a direct bearing on the health of patients? Yes
  2. Is the outcome or topic something that patients/clients/population groups would care about? Yes
  3. Is the problem addressed in the review one that is relevant to dietetics practice? Yes
  4. Will the information, if true, require a change in practice? ???
Validity Questions
  1. Was the question for the review clearly focused and appropriate? Yes
  2. Was the search strategy used to locate relevant studies comprehensive? Were the databases searched and the search termsused described? Yes
  3. Were explicit methods used to select studies to include in the review? Were inclusion/exclusion criteria specified andappropriate? Wereselectionmethods unbiased? Yes
  4. Was there an appraisal of the quality and validity of studies included in the review? Were appraisal methodsspecified,appropriate, andreproducible? Yes
  5. Were specific treatments/interventions/exposures described? Were treatments similar enough to be combined? Yes
  6. Was the outcome of interest clearly indicated? Were other potential harms and benefits considered? Yes
  7. Were processes for data abstraction, synthesis, and analysis described? Were they applied consistently acrossstudies and groups? Was thereappropriate use of qualitative and/or quantitative synthesis? Was variation in findings among studies analyzed? Were heterogeneity issued considered? If data from studies were aggregated for meta-analysis, was the procedure described? Yes
  8. Are the results clearly presented in narrative and/or quantitative terms? If summary statistics are used, are levels ofsignificance and/or confidence intervals included? Yes
  9. Are conclusions supported by results with biases and limitations taken into consideration? Are limitations ofthe review identified anddiscussed? Yes
  10. Was bias due to the review's funding or sponsorship unlikely? Yes