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

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

To promote healthy dietary and lifestyle habits in children, with the ultimate aim being to minimize the risk of development of CVD in adult life.

Aims of first 3 years of intervention were to increase the awareness of parents and children predominantly on issues related to healthy diet and regular physical activity and to encourage and support pupils to improve their dietary habits & physical fitness.

Further aim was to establish an appropriate environment at both schools and home for support of the children’s expected behavioral changes.

Inclusion Criteria:

All pupils in the first grade of the selected schools in 1992.

Exclusion Criteria:

Not specified

Description of Study Protocol:

Data collection took place during September – November 1992 and September – November 1995. Data collection from the children included: health knowledge scores, anthropometric measurements, physical fitness indices & biochemical examinations. Parents provided information:

  1. by completing coded questionnaires regarding personal characteristics & issues related to both their own health habits & knowledge
  2. by completing a questionnaire regarding weekly frequency of consumption of various foods &, in a random sample of 30% of the baseline cohort, by providing a record of the weights of all foods consumed by their child over a 3-day period; and
  3. by completing forms relating to their child’s physical activity levels.

The health and nutritional components of the program were conducted by classroom teachers and incorporated 13 to 17 h of teaching over the academic year (teacher delivered). The physical fitness and activity components of the program included practical sessions as well as classroom sessions were delivered by PE instructors. The control group did not have any health education intervention. Parental involvement – meetings were organized at which parents in the intervention group were given a file containing their child’s medical screening results. Parents were encouraged to modify their own dietary habits in addition to those of their children. They were also advised to support their offspring in their physical activity rather than encourage sedentary behavior.

Statistical Analysis:

Mixed model analyses.

Data Collection Summary:

Dependent Variables

  • Health Knowledge (multi-choice questionnaire),
  • Dietary Intake (parent-reported 3-day weighed food record),
  • Physical Activity (standardized activity interview completed by parent/guardian),
  • Fitness Level (EUROFIT Tests Protocol includes sit & reach test, sit ups, handgrip test, standing broad jump test, 20-m shuttle run test),
  • Anthropometric Measurements - BMI (based on measured ht & wt0, Triceps, biceps, subscapular & supraliac skinfold thickness (measured following standardized procedures)
  • Biochemical Indices – Triglycerides, Total Cholesterol, High-Density Lipoproteins Cholesterol (measured following standardized procedure).

Independent Variables

  • Intervention group verses Control group (see study protocol).

Control Variables

  • Baseline values
  • Sex
  • Parental education levels
  • Increase in height and Initial BMI
Description of Actual Data Sample:

Original Sample: 4,171 pupils registered in the first grade in the 2 counties of Crete. The 1,510 pupils registered in a third county served as controls. A random subsample of 21 of the schools initially examined was drawn (12 intervention & 9 controls); 579 pupils.

Withdrawals/Drop-Outs: Transferal to another school & absence on the examination day.

Final Sample: 471 were available for rescreening; only 76 intervention children & 63 control children had completed 3-day weighed food records at baseline and at rescreening time.

Location: Crete, Greece (intervention: Heraklio & Rethymno; control: Hania)

Race/Ethnicity: not specified

SES: 3 counties are very similar with regard to population distribution, socioeconomic status of residents, etc.

Summary of Results:

Intervention vs Controls at Baseline

The intervention group had significantly higher average values of TC and LDL than the controls.

The mean 20mSRT measurement at baseline in the intervention group was significantly lower than in the control group.

There was also strong evidence that the control group pupils had higher health knowledge scores at baseline. There were also differences of the same direction in the parental health knowledge scores. None of the other baseline measurements differed significantly between groups.

Biochemical Indices

Following 3-years of intervention, total serum cholesterol levels had displayed a decrease in intervention group while they had increased in control group (P=0.001).

There was a similar effect displayed in LDL levels, which decreased on average in the intervention group while in controls the average LDL levels exhibited an increase (P=0.001).

Anthropometric Indices

Children from the intervention group were found to have had a significantly higher average gain in height over 3-year period, compared to control group pupils (P=0.009).

Control group pupils had a significantly higher change in mean BMI than intervention group pupils and suprailiac skinfold (P<0.05) when adjusting for the change in height, sex, parental educational group & baseline values.

Dietary Intake

No significant differences between intervention & control group in weekly food consumption levels (3-day weighed food record) at follow-up when controlling for baseline levels, sex, BMI & parental education.

Authors suggested the lack of significant dietary changes may be the result of the small proportion of subjects providing dietary recorders.

Moderate-Vigorous Activity

Intervention group pupils displayed a significantly greater increase in time spent in MVPA over the 3-year period, compared to control group (P<0.0005).

Fitness Indices

There were significantly greater mean increases in both SBJ – standing broad jump test and SUP – sit up measurements over the 3-y period in the intervention group, when controlling for initial values, sex, change in height, parental education group & initial BMI.

Children’s Health Knowledge

Increases in the children’s mean health knowledge scores by midterm were significantly higher in intervention group.

Parent’s Health Knowledge

There were no significant differences in increases in parents’ health knowledge scores between the two groups.

Author Conclusion:

The significant changes observed in the intervention group compared to the control group can be attributed to the high parental participation in the program, the baseline data of the overall population (health knowledge, obesity, serum lipids, and dietary and exercise habits) which had room for significant improvements and the organized and expanded PE classes. Combining the health education program with the PE classes optimized the physical activity and fitness as well as the nutritional component of the program thus allowing more hours of intervention with the least possible interference for the remainder of the curriculum. Such interventions provide an important model for school-based health promotion programs for primary prevention of CVD, with out requiring substantial school time or new resources.

Funding Source:
Government: EU, Mediterranean Integrated Program of Crete, General Secretary of the Periphery of Crete
University/Hospital: University of Crete (Greece)
Foundation associated with industry:
Reviewer Comments:


  • Parental participation.


  • Sampling procedure used to allocate the schools was not a completely randomized procedure.
  • Small sample with both baseline and 3-year follow-up data on dietary intake.
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) N/A
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? N/A
  3. Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? N/A
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) N/A
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? N/A
  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.) N/A
  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%.) N/A
  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? N/A
  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? N/A
  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? No
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? Yes
  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