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

Study Design:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
  • To conduct a controlled trial of a comprehensive, school-based program for elementary school children
  • To evaluate the combination of behavior modification and nutrition education administered in the school setting as a form of treatment.
Inclusion Criteria:
  • Children ages five to 12 years from grades kindergarten through five in a public elementary school in Ft. Myers, FL
  • At least 10% above average body weight for their age, sex and height
  • Free of medical conditions or not taking any medications that would influence body weight
  • Not involved in another formal weight reduction program
  • Signed informed consent from parent.
Exclusion Criteria:

None specified.

Description of Study Protocol:


  • Weight and height measured by nurse’s aide on all children in the school
  • Permission slips were sent to the parents of 68 children who were at least 10% overweight
  • The nurse's aid phoned parents who did not respond initially and urged enrollment
  • Parental permission obtained for study participants, a total of 63 children.  

Intervention Based on Social and Educational Factors

  • 10-week program
  • Four guides were prepared for 1) students, 2) teachers, 3) parents and 4) administrators, containing information on behavior modification, nutrition and physical activity.  Included instructions for:
    • Recording food intake
    • Limiting situations for eating
    • Slowing the rate of eating
    • Improving attitudes
    • Rewarding changes in eating and physical activity
    • Contracting
  • Nurse’s aide weighed children weekly, kept graphs of weight changes, distributed materials, held meetings with parents, established awards ceremony, coordinated activities
  • Parents taught to praise behavior changes, encouraged to attend meetings, spoke via telephone with nurse’s aide, given suggestions for increasing activity in children
  • Teachers instructed in encouragement methods, worked with parents and non-obese children to establish positive climate
  • Daily physical education classes for all children – instructor changed emphasis from competitive to non-competitive activities
  • Special diet meal offered to program participants during school lunch. Diet meal contained approximately 500 calories in contrast to regular school lunch, which contained approx. 800 to1,000 calories, consisted of salad plate with protein, low calorie dressing, bread, fruit, low fat milk.
  • Children in program met with nurse’s aide in small groups, encouraged to help one another. Weight charts posted so everyone’s progress could be followed. Non-program children encouraged to support changes in weight and eating patterns in peers.
  • School principal encouraged school personnel to play an active role.

Comparison Group

  • Children used as own controls by analyzing school weight records for three years prior to program
  • Second method of comparison used obese children who did not experience the program
  • The comparison group formed from two sets of children – children with parents who refused permission (N=5) and children from another school similar in SES and race/ethnicity ratio (N=9).

Statistical Analysis

Analysis of variance (ANOVA) and covariance (ANCOVA) to compare program and control children.

Data Collection Summary:

Dependent Variables

  • Weight (balance beam scale)
  • Height (before and after the program)
  • Change in body weight (before the start of the program, each week during the program) 
  • Change in percentage overweight (percentage above average weight for child’s age, sex, height – norms from American Child Health Association)

Independent Variables

Program vs. non-program participation

Control Variables

  • Initial weight
  • Initial percentage overweight.
Description of Actual Data Sample:
  • Original sample: 68 children identified by nurse’s aide as at least 10% overweight from 650 (of 667) children measured in school
  • Withdrawals/Drop-outs: Parental permission denied for five of 68 overweight children
  • Final sample: 77 children (37 boys, 40 girls) - 63 program children and 14 controls (controls from five children whose parents refused permission plus nine children chosen randomly from nearby school similar in SES and ethnicity ratio).
  • Location: Ft. Myers, FL
  • Race/Ethnicity: 62 white (81%), 15 black (19%)
  • SES: Predominantly lower middle class.
Summary of Results:
  • Program children:
    • Were heavier than control children at baseline (45.9kg vs. 37.5kg)
    • Lost more weight than control children (P<0.0001): Of 63 program children, 60 lost weight (95.2%), compared to three of 14 control children (21.4%). Mean weight changes were loss of 4.4kg for program children, gain of 1.2kg for control children (P<0.0001).
    • Were more like to show a decrease in percentage overweight (P<0.0001): 96.8% of program children compared to 28.6% control children. Mean changes in percentage overweight were decrease of 15.4% for program children, increase of 2.8% for control children
    • Showed steady increase in degree of obesity during three years before program; trend was reversed during program
  • Not only did control children not lose weight, but the weight loss in the program children stands in contrast to the history of weight gain before the program
  • Boys and girls did not differ in weight loss or change in percentage overweight
  • Positive association between initial weight and weight loss (heavier children lost more weight); positive association between initial percentage overweight and change in percentage overweight (r=0.37, P<0.01)
  • Older children tended to lose more weight (r=0.34, P<0.01) and larger percentage (r=0.33, P<0.01) than younger children.
Author Conclusion:

This program focused on behavioral methods, which may be helpful in promoting lasting changes in eating and physical activity patterns. Also, program emphasized child’s social network; broad base of social support may be necessary for success.

  • 95% of children in program lost weight, even though weight gain was expected due to developmental growth
  • 97% of program children showed reductions in percentage overweight, indicating decreased obesity
  • Mean weight loss (4.4kg) and mean decrease in percentage overweight (15.4%) are clinically significant reductions
  • 71% of control children showed increases in weight and percentage overweight
  • Children in program showed significantly greater weight changes than control children
  • When using children as own controls, program children reversed three-year trend of weight gain, control children interrupted stable degree of obesity by gaining weight slightly.


  • Strong support in school – all 63 children completed program
  • Children were used as there own control for some of the outcome measurements.


Control children were not selected randomly and not drawn from same population, thus constituted a “quasi” control group rather than traditional control.

Funding Source:
Government: USDA to the State of Florida Department of Education; NIMH and NHLBI
Reviewer Comments:
  • While this study produced positive initial results, it is not known if weight loss or percentage overweight was maintained after the program ended
  • Different procedures may be necessary for weight maintenance over time in this same group.
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? No
  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? No
  2.4. Were the subjects/patients a representative sample of the relevant population? No
3. Were study groups comparable? No
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) No
  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.) 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? N/A
  4.1. Were follow-up methods described and the same for all groups? N/A
  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? N/A
  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.) Yes
  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? No
  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? No
  6.6. Were extra or unplanned treatments described? No
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? N/A
  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? No
  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)? N/A
  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? N/A
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