PWM: School-based Programs to Prevent Overweight (2006)

Study Design:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
To evaluate the effects of environmental, policy, and social marketing interventions on physical activity and fat intake of middle school students on campus
Inclusion Criteria:
None provided (surveys sent to randomized selection of students within schools).
Exclusion Criteria:
None provided
Description of Study Protocol:


schools randomly assigned within district to intervention (n=12) or control (n=12); method of randomization not described

Environmental/social marketing intervention (no classroom education)

  • Change school foodservice to increase the availability of low-fat food choices
    • 11 hr training for foodservice staff
    • Increased kitchen equipment (all schools received $500)
    • Education packets for student store mgrs
    • Identified vendors of low-fat items
    • Vendor fairs & taste testing of low-fat items
    • Recipes modified/ ingredients substituted
    • Salad bars opened
    • Hours of student store reduced
    • On-site visits for progress monitoring
    • Nutrition policy changes (three 90-min health policy meetings with stakeholders)
    • Students health committees (also for PA)
    • Poster-style newsletters to highlight foodservice changes
    • Ideas for low-fat bag lunch items printed in schools’ parent newsletters
    • Healthy lunch contests
    • Signs & foodservice staff promoted changes
  • Improve daily PE quality and promote PA throughout school day
    • New PE curriculum materials
    • Five 3-h staff training sessions + on-site assistance/feedback
    • Increased supervision
    • Increased equipment (all schools received $1000)
    • Increased organized activities before/after school & after lunch (all schools received $2000 for programs or equipment)
    • PA policy changes (see above)
    • Poster-style newsletters to highlight changes in PE
    • Advertising of PA programs through flyers, school bulletins, parent newsletter, PTA meetings

Statistical Analysis

  • Randomized regression models – to examine change in school-level outcomes by group over time (baseline, year 1, year 2)
  • Randomized regression models with data aggregated by school – to examine changes in survey-based outcomes by group over time
  • Effect sizes (change in intervention schools minus change in control schools/ pooled SD of change) examined from baseline to year 2; effect sizes interpreted as small (0.20), medium (0.50), and large (0.80)
Data Collection Summary:

Timing of Measurements

Dependent Variables - school-based analyses

  • PE energy expenditure
    • System for Observing Fitness Instruction time [SOFIT] method by trained observers
    • 3 random days at baseline and 2 days during each intervention semester
    • 1947 classes observed
  • Leisure time energy expenditure
    • System for Observing Play and Leisure Activity of Youth [SOPLAY] method by trained observers
    • 3 random days at baseline and 2 days during each intervention semester
    • 5046 observations
  • Total fat & saturated fat in Type A breakfast/lunch, a la carte foods & student store foods
    • Menu documentation of foods >1 g total fat per serving by foodservice staff; recipes, food labels & sales data analyzed for same # days as above)
    • 3 random days at baseline and 2 days during each intervention semester
  • Total fat & saturated fat brought in school bag lunches
    • Foods & serving sizes recorded by trained observers
    • % of students bringing bag lunches estimated from student surveys
    • 3 random days at baseline and 2 days during each intervention semester
    • 18 lunches per day

Dependent – survey-based analyses

  • Moderate to vigorous PA outside of PE (survey of minutes participated in past 7 d in 32 activities)
  • Sedentary activity (survey of minutes participated in past 7 d in 9 sedentary activities)
  • Fatty food intake (survey of amount consumed in past day of 31 high-fat foods/beverages and avoidance of fat in family food preparation)
  • BMI (self-reported height and weight)


Independent Variables

Middle-School Physical Activity and Nutrition (M-SPAN) study (see above)

Control Variables

Gender (separate analyses)


Description of Actual Data Sample:


Original Sample: 48 public middle schools invited to participate; first half that agreed were accepted


Withdrawals/Drop-Outs: not described (not applicable given study design, but mobility within schools would have been helpful to know)

Final Sample: 24 middle schools with mean of 1109 + 356 students per school; individual surveys to random samples of student/parent pairs at baseline (1678; response rate = 72%) and end of study (1434; response rate = 60%), grades 6-8

Location: San Diego County, CA

Duration:  2 y, Spring 1997 – Fall 1999

Race/Ethnicity:  56% (another place says 57%) White, 44% non-White, but note that Whites and males underrepresented in individual surveys

SES:  39.5% received free or reduced school meals


Summary of Results:

No significant differences between groups at baseline on school characteristics (factors not described) or outcome variables

Physical activity

  • Increase (kcal/d/child) for total intervention group at school (p<.009; large effect size = 0.93)
  • Increase  for boys at school (p<.001)
  • No change for girls at school
  • Boys in intervention schools increased about equally in PE and leisure school activity; girls in intervention schools increased activity mainly through PE
  • No change in moderate to vigorous physical activity outside of PE from survey data
  • No change in sedentary activity from survey data


  • No change for total or saturate fat at school
  • No change in fatty foods consumed outside of school from survey data
  • No change in parental fat avoidance from survey data


decreased BMI for boys (p<.05), but not girls

Author Conclusion:

Environmental and policy interventions were effective in increasing physical activity at school among boys but not girls. The interventions were not effective in reducing fat intake at school.  School environmental and policy interventions have the potential to improve health behavior of the student population, but barriers to full implementation need to be better understood and overcome.

The lack of changes outside of school was not surprising, as these environments were not targeted by the interventions.

The significant intervention effect on boys’ BMI suggests that boys may have increased their physical activity enough to produce physiologic effects.

Funding Source:
University/Hospital: San Diego State University, University of California
Reviewer Comments:


Large sample size, 2 y duration, one of few environmental intervention studies evaluated, multiple components targeted


Self-reported BMI, no blinding of observers, unlikely that intervention intensity with respect to foodservice changes were sufficiently large to produce physiologic effects, survey data included unknown number of same individuals pre/post intervention, unclear amount of exposure (e.g., amount of time survey respondents at f/u had been as school during previous 2 y).

Quality Criteria Checklist: Primary Research
Relevance Questions
  1. Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies) Yes
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? Yes
  3. Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? Yes
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
Validity Questions
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? ???
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? ???
  1.3. Were the target population and setting specified? ???
2. Was the selection of study subjects/patients free from bias? Yes
  2.1. Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study? ???
  2.2. Were criteria applied equally to all study groups? ???
  2.3. Were health, demographics, and other characteristics of subjects described? ???
  2.4. Were the subjects/patients a representative sample of the relevant population? ???
3. Were study groups comparable? Yes
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) ???
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? ???
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) ???
  3.4. If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis? ???
  3.5. If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.) ???
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? ???
4. Was method of handling withdrawals described? Yes
  4.1. Were follow-up methods described and the same for all groups? ???
  4.2. Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.) ???
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? ???
  4.4. Were reasons for withdrawals similar across groups? ???
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? ???
5. Was blinding used to prevent introduction of bias? No
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? ???
  5.2. Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.) ???
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? ???
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? ???
  5.5. In diagnostic study, were test results blinded to patient history and other test results? ???
6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? Yes
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? ???
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? ???
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? ???
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? ???
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? ???
  6.6. Were extra or unplanned treatments described? ???
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? ???
  6.8. In diagnostic study, were details of test administration and replication sufficient? ???
7. Were outcomes clearly defined and the measurements valid and reliable? No
  7.1. Were primary and secondary endpoints described and relevant to the question? ???
  7.2. Were nutrition measures appropriate to question and outcomes of concern? ???
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? ???
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? ???
  7.5. Was the measurement of effect at an appropriate level of precision? ???
  7.6. Were other factors accounted for (measured) that could affect outcomes? ???
  7.7. Were the measurements conducted consistently across groups? ???
8. Was the statistical analysis appropriate for the study design and type of outcome indicators? No
  8.1. Were statistical analyses adequately described and the results reported appropriately? ???
  8.2. Were correct statistical tests used and assumptions of test not violated? ???
  8.3. Were statistics reported with levels of significance and/or confidence intervals? ???
  8.4. Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)? ???
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? ???
  8.6. Was clinical significance as well as statistical significance reported? ???
  8.7. If negative findings, was a power calculation reported to address type 2 error? ???
9. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? ???
  9.2. Are biases and study limitations identified and discussed? ???
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? ???
  10.2. Was the study free from apparent conflict of interest? ???