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

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

The purpose of this study is to examine whether or not a school-based intervention is effective in reducing risk factors for obesity in children age seven to 11 years.

Inclusion Criteria:
  • Children age seven to 11 years
  • Recruited from ten Leeds, UK primary schools.


Exclusion Criteria:

Not described.


Description of Study Protocol:


Children were recruited from ten Leeds state primary schools outside of the inner city area.


  • The researchers randomized the children to receive intervention or to serve as a control school using a coin toss
  • The intervention schools received the Active Program Promoting Lifestyle Education in school (APPLES). This program consisted of teacher training, school meal modifications and the design and implementation of school action plans to promote healthy eating and physical activity over one school year (September 1996 to July 1997).
  • The control schools continued with their usual health curriculum, with no intervention.


APPLES included the following aspects:

  • One year multi-disciplinary, multi-agency program designed to influence diet and physical activity
  • Used a population approach supported by the Health Promoting Schools philosophy and targeted the whole school community (e.g., parents, teachers and catering staff)
  • Based on school action plans designed by the individual schools on the basis of their perceived needs
  • Provided training, resources, input and support to teachers.

Statistical Analysis

A power calculation indicated that the study would have 80% power to detect an underlying difference in means of a normally distributed outcome measure of greater than 1.8 SD at the 5% significance level and 65% power to detect a difference of 1.5 SD.


Data Collection Summary:

Dependent Variables

  • Growth measure: Weight was taken without shoes or sweatshirt using portable scales. Height was measured by a using a free stadiometer. Body mass index (BMI) was then calculated. Overweight was defined as BMI greater than 85th percentile and obese was defined as BMI greater than 95thpercentile.
  • Dietary information: Frequency of consumption of foods high in fat, foods and drinks high in sugars, fruit and vegetables was measured using 24-hour recall and three-day food diaries
  • Physical activity: Frequency and sedentary behavior was measured using a questionnaire
  • Psychological measures: Assessed using three validated tols to evaluate effect of intervention on psychological well-being. 

Independent Variables

Intervention or control school.

Control Variables

Researchers adjusted for the characteristics of the individuals (i.e., sex, age, baseline BMI and outcome of interest at baseline) and the intervention status of the five pairs of schools.

Statistical Analysis

  • A multi-level statistical model was used to assess changes in BMI, diet, physical activity and psychological well-being
  • The Castlemead growth package was used to convert BMI, height and weight to standard deviation scores.
Description of Actual Data Sample:
  • Original sample: N=636 children (314 intervention, 322 comparison)
    • Of the 636 children who were participated in the initial evaluation, 613 (97%) children were measured at baseline, 595 (94%) at the end of the intervention period
    • 404 (63%) completed three-day food and physical activity diaries at baseline and 407 (64%) completed three-day food and physicial activity diaries at the end of the study.
  • Final sample: N=203 to 303 children at 12 months (350 males, 286 females) (NOTE: total # different than in abstract)
  • Location: Outside the inner city area of Leeds, UK
  • Race/Ethnicity: Schools had one to 42% of children from ethnic minorities
  • SES: Schools had seven to 29% of children entitled to free school meals
  • Mean age: 8.4 years.
Summary of Results:
  • Adiposity: Overall, there was no difference in score between the intervention and control children at the end of the year 
  • Diet:
    • Analysis of 24-hour recall showed that the intervention children had higher vegetable intakes at the end of the study. The weighted mean difference 0.3 indicates on average one-third of a portion more a day. As the mean baseline was only 0.6 portions per child per day, this difference is equivalent to 50% of baseline intake. The same difference was seen for the overweight and obese children.
    • A significantly lower fruit intake was observed in the obese children from the intervention schools compared to the obese children from the control schools (24-hour recall)
    • According to the three-day diaries, there was a higher intake of foods and drinks high in sugar in overweight children in the intervention group compared to overweight children in the control group
  • Physical activity: There was no significant difference in physical activity or sedentary behavior for the sample as a whole. Sedentary behavior increased by one-third in the overweight children in the intervention group compared with overweight control children.
  • Psychological measures: The only significant difference in psychological measures was a small increase in global self-worth for obese children in the intervention schools.
Author Conclusion:
  • The author concluded that this study was successful in changing the behavior of schools and attitudes of the children, although the study did not reduce risk factors for obesity
  • Longer term studies need to be conducted to achieve greater success with weight loss.
Funding Source:
Government: Northern and Yorkshire Region Research and Development Unit
Reviewer Comments:
The outcome measurements could not be obtained blind to the schools’ intervention status.
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? Yes
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
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? Yes
  2.2. Were criteria applied equally to all study groups? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? Yes
  2.4. Were the subjects/patients a representative sample of the relevant population? Yes
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) Yes
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? Yes
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) Yes
  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? N/A
  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.) Yes
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? N/A
4. Was method of handling withdrawals described? Yes
  4.1. Were follow-up methods described and the same for all groups? Yes
  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%.) Yes
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? Yes
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? N/A
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? No
  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.) No
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? N/A
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? Yes
  5.5. In diagnostic study, were test results blinded to patient history and other test results? N/A
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? Yes
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? Yes
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? Yes
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? Yes
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? N/A
  6.6. Were extra or unplanned treatments described? N/A
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? Yes
  6.8. In diagnostic study, were details of test administration and replication sufficient? N/A
7. Were outcomes clearly defined and the measurements valid and reliable? Yes
  7.1. Were primary and secondary endpoints described and relevant to the question? Yes
  7.2. Were nutrition measures appropriate to question and outcomes of concern? Yes
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? Yes
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? Yes
  7.5. Was the measurement of effect at an appropriate level of precision? Yes
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  7.7. Were the measurements conducted consistently across groups? Yes
8. Was the statistical analysis appropriate for the study design and type of outcome indicators? Yes
  8.1. Were statistical analyses adequately described and the results reported appropriately? Yes
  8.2. Were correct statistical tests used and assumptions of test not violated? Yes
  8.3. Were statistics reported with levels of significance and/or confidence intervals? Yes
  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)? No
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? Yes
  8.6. Was clinical significance as well as statistical significance reported? Yes
  8.7. If negative findings, was a power calculation reported to address type 2 error? Yes
9. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? Yes
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes