PWM: School-based Interventions (2011)

Study Design:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:

To examine the efficacy of school-based programs for reducing childhood overweight or obesity.

Inclusion Criteria:
  • Published between January 1, 1990 and December, 2005
  • Experimental or quasi-experimental design
  • Primary or secondary outcomes reported in terms of BMI
  • Outcomes reported at least six months post-baseline
  • Curricular or environmental in design (as opposed to extracurricular)
  • Preventive interventions involving both overweight and normal-weight children.
Exclusion Criteria:

Specific exclusions not given beyond not meeting inclusion criteria

Description of Study Protocol:

Identification of studies

  • Search of studies published from January 1, 1990 through December, 2005
  • Databases searched:
    • PubMed
    • Biological Abstracts
    • Education Abstracts
    • Other studies were sought and identified through references from previous review articles and primary publications, and from personal communication with obesity researchers
  • Search Terms: Alone and in combination: School, obesity, overweight, weight, prevention, nutrition, physical activity, trial, BMI, blood pressure, cholesterol, environment, child, adolescent, food choices, metabolic syndrome.

Evaluation of study quality

  • Evaluated using criteria of the GRADE working group
  • Design of a study, methodological strengths and weakness, and significance of findings used to characterize study
  • Baseline grade of one to four given, adjusted based on confounders, sample size, power, directness, statistical techniques and effect size
  • Each study assessed independently by two of the authors
  • Inconsistencies settled by consensus discussion
  • Consensus in assignment of overall grading score was uniform between the two raters.


Systematic review 

Statistical Analysis

No meta-analysis or quantitative analysis

Data Collection Summary:

Dependent Variables

Reduction in childhood overweight or obesity

Independent Variables

  • School-based nutrition program
  • School-based physical activity program
  • Combined nutrition and physical activity program.

All programs compared to control comparison

Control Variables

Not applicable


Description of Actual Data Sample:
  • Initial N: Number of articles identified not given
  • Attrition (final N): N=14 articles included
    • Diet alone: N=1
    • Physical activity alone: N=2
    • Combined: N=11
  • Age: Not specified
  • Ethnicity: Not applicable
  • Other relevant demographics: Not applicable
  • Anthropometrics: Not applicable
  • Location: Not specified.


Summary of Results:

Key Findings

12 studies reported significant improvement in at least one measure of dietary intake, physical activity and sedentary behavior.

Nutrition component only vs. control (one study)

Significant reduction in carbonated beverages of 0.7 drinks per three days; no BMI outcomes (grade 3 study)

Physical activity component only vs. control (two studies)

  • Significant improvement in time spent in moderate-vigorous physical activity; no effect on BMI (grade 2)
  • Significant reduction in odds ratio for increased BMI in kindergarten girls only (grade 3).

Combined nutrition and physical activity vs. control (11 studies) 

Measures of Overweight

  • Significant results for outcomes related to BMI: N=4; or triceps skinfold: N=2;  two were significant in boys only, one was significant in girls only
    • In those studies, significant outcomes related to physical activity: N=5, and for one study, no significant effect was reported for physical activity
    • One study that showed significant improvements in dietary measures and change in overweight in the physical activity X nutrition group.

Behavioral Measures

  • Significant results related to measures of physical activity: N=7 (five of which showed changes in measures of overweight)
  • Significant improvements in dietary measures: N=4, one of which also showed an effect on measures of overweight (one of which showed changes in measures of overweight)
  • Significant improvements in both physical activity and dietary measures: N=2 (no effect on overweight in one study)
  • Change in measures of overweight in one study with no report regarding improvements in physical activity or dietary measures. 

 Summary of results of studies with combined nutrition and physical activity:

  • Significant reduction in overweight percentage in middle-school girls (no effect for boys) 
  • Adjusted OR for overweight of 0.47, mediated by reduction in television viewing (grade 4)
  • Small increase in self-reported physical activity among Native American children in intervention group; no effect for overweight (Grade 2)
  • Child and Adolescent Trial for Cardiovascular Health (CATCH) trial (two studies)
    • RCT (grade 3)
      • Significant increase of 13 minutes in daily moderate-to-vigorous physical activity
      • Significant decrease of 2.5% in school lunch energy from fat
      • At three-year follow-up, increased physical activity and decreased fat intake persisted compared to controls
      • No effect for overweight outcomes
    • Quasi-experimental effectiveness trial (grade 2)
      • Mexican-American community
      • Significant relative reduction in overweight prevalence of 11% in girls and  8% in boys
      • Small, but significant increase in physical activity in intervention group
  • Significant relative reduction in in BMI in boys of 0.64kg/m2 with a significant increase in moderate-to-vigorous activity; no effect for girls (grade 3 RCT)
  • Significant increase in fruit or vegetable intake (two grade two RCTs); no significant effects for overweight
  • Significant 6% increase in physical activity in intervention group; no effect for overweight (grade 2)
  • Significant reduction in triceps skinfold thickness of 1.9mm in intervention subjects compared to controls at one-year follow-up (grade 2 study); four-year outcome data showed a significant relative reduction in obesity prevalence of 13.2% in girls
  • Significant 3.2% reduction in body fat among overweight subjects in post hoc analysis
  • Significant improvements in daily physical activity and television viewing time
  • Significant reduction of 0.3kg/m2 for BMI and  0.1 units for z-BMI in boys only (grade 2 quasi-experimental study)
  • Significant differences in post-intervention triceps skinfold in boys and girls who received physical education plus school nutrition (grade 2); significant improvements in dietary measures of some food groups.

Quality of Evidence

The quantity and strength of evidence for the interventions were insufficient to draw specific conclusions as to their effectiveness for weight outcomes. At present, the overall quality of evidence is weak.

  • Weak (grade 2): N=10
  • Moderate (grade 3): N=3
  • Strong (grade 4): N=1.
Author Conclusion:
  • At present, there is insufficient evidence to provide strong guidance as to the benefits of school-based overweight prevention programs due to a limited number of published studies as well as methodological concerns that limit the validity of and comparability between those identified.
  • Qualitative analysis suggests programs grounded in social learning may be more appropriate for girls, while structural and environmental interventions enabling physical activity may be more effective for boys
  • High-quality evaluation protocols should be considered essential components of future programs.
Funding Source:
Other: Not specified
Reviewer Comments:
  • Overall, good review
  • Synthesis related to type, length, intensity etc. of interventions, especially physical activity, would be helpful.
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? N/A
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