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

Study Design:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
  1. To compare change in weight among program participants to change among children volunteering for, but not receiving the program (random control) .
  2. To compare change  in weight among random controls to change among a non-volunteering group (self-selected control) to evaluate the adequacy of the quasi-experimental approach.
Inclusion Criteria:

Children 10% or more overweight from three junior high schools who received parental permission to participate (percentage of deviation from mean weight for height and age from US Dept. of Health, Education and Welfare publication, 1973).

Exclusion Criteria:
Description of Study Protocol:

Consenting children ranked according to percentage overweight and randomly assigned from stratified blocks to treatment (n=30) or no treatment (n=25). Self-selected control group formed of those children whose parents declined permission to participate (n=59).

Treatment consisted of 12 weekly 45 minute group meetings; children excused from class to attend meetings. Heights and weights recorded pre- and post-treatment and every 3 weeks; control heights and weights measured pre- and post-treatment.

All sessions conducted by female physical education instructor.

Goal of weight program was to encourage gradual change in eating and exercise habits.

Children self-monitored food intake and exercise, encouraged to problem solve. Food exchange plan was taught emphasizing 3 balanced meals/day; taught to slow rate of eating, limit times and places of eating, change serving and preparation habits.

During half of sessions children practiced aerobic activities, discussed ways to increase duration and frequency of outside exercise.

Children rewarded with lottery tickets for each half pound lost to win recreational passes.

Parent participation elicited through four ½ hour evening group meetings to receive feedback concerning child’s program and discuss ways to reinforce new eating and exercise behaviors.

Statistical Analysis:

Analysis of covariance (ANCOVA) to detect significant differences in weight change.

Data Collection Summary:

Dependent Variables

  • Weight
  • Height
  • Mean percentage overweight

Independent Variables

  • Treatment, or no treatment
  • Self selected control or random control
  • Parent participation

Control Variables

  • Age
  • Sex
  • Pre-treatment weight
  • Pre-treatment percentage overweight
Description of Actual Data Sample:

Original Sample: 114 children in 3 junior high schools

Withdrawals/Drop-Outs: 59 did not receive parent permission (52%)

Final Sample: 55 children (30 in treatment group, 25 in no treatment group); 59 as self-selected control group.

47% of treatment group, 44% of control group, 44% of self-selected controls were male.

Mean ages were 12.9 +/- 1.3 years in treatment group, 13.3 +/- 1.3 years in no treatment group, 13.2 +/- 0.91 years in self selected group.

Location: Not specified, possibly Williamsport, PA.

Race/Ethnicity: Not specified.

SES: Not specified

Summary of Results:

In treatment group, average pre-treatment weight was 152.05 lbs, mean percentage overweight was 43.93%.

In control group, average pre-treatment weight was 157.81 lbs and mean percentage overweight was 47.47%.

Over 12 week program, both groups gained weight and height.

Treatment group gained 1.26 +/- 6.54 lbs, grew 0.72 +/-.56 in. and decreased percentage overweight 5.71 +/-9.04%.

Control group gained 7.32 +/-7.38 lbs, grew 0.80 +/-.65 in. and increased percentage overweight 2.41 +/- 7.5%.

Differences in weight change and percentage overweight change significant.

Self-selected controls comparable in age, pre-treatment weight, percentage overweight to random controls. Twelve-week height, weight and percentage overweight changes not significantly different from random controls.

25 self-selected children matched for age, sex, pre-weight and pre-percentage overweight to random controls; no significant differences in 12-week change revealed.

One third of parents attended a parent meeting; influence of parent participation explored in post hoc fashion. Children with attending parents decreased percentage overweight 9.50 +/- 10.53% while children with non-attending parents decreased percentage overweight 3.94 +/- 5.18%. Statistical analysis showed trend in favor of children whose parents attended at least one meeting; correlation between number of meetings attended and change in percentage overweight significant.

Author Conclusion:

Data indicate that a behavioral approach is effective in inducing short-term weight changes in a school-based intervention.

Average child in treatment did not actually lose weight, but changes in height may have masked effect of treatment on weight.

Trend for children with participating parents to decline more in percentage overweight than children with non participating parents; parental participation significantly correlated with outcome.

Post-treatment differences between random and self-selected controls nonsignficant; results support use of nonparticipating, nonconsenting children as controls in studies of adolescent weight loss
Funding Source:
Government: Williamsport area School District
University/Hospital: University of Health Sciences/Chicago Medical School
Reviewer Comments:


  • lack of data on long term weight changes
  • lack of demographic information
  • In this age group, the stage of puberty will also affect % body fat; it was not assessed.
  • no information about how weight and height measurements were obtained
  • statistical analysis not fully described
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? No
  2.4. Were the subjects/patients a representative sample of the relevant population? ???
3. Were study groups comparable? ???
  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? ???
  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? No
  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? N/A
  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.) 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? 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? 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? ???
  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? ???
  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? ???
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? No
  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? N/A
  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? ???
  10.1. Were sources of funding and investigators' affiliations described? No
  10.2. Was the study free from apparent conflict of interest? ???