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

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

(Author’s words)

  1. To implement a nutrition and activity program for elementary school children consistent with the guidelines for Healthy People 2000 that can be integrated within the current nutrition and activity programs with existing personnel and with minimal training and additional resources
  2. To demonstrate the effectiveness of the nutrition and activity program in: a) modifying the diet in accordance with guidelines for Healthy People 2000 (i.e., lower intakes of fat, cholesterol, sodium, increased intakes of fiber); b) decreasing weight gain in children who are overweight; c) increasing physical fitness; d) increasing the knowledge and awareness of diet in health.
  3. To demonstrate that the nutrition and activity program will produce favorable changes in markers of health risk which include body weight, body composition, fitness, blood lipids, hypertension and insulin/glucose
  4. To demonstrate that an effective program of nutrition consistent with the guidelines for Healthy People 2000 is received equally or better than the existing nutrition program
  5. Demonstrate that a program of nutrition, physical activity and education will impact favorably on the student’s lifestyle away from school by promoting wise food choices and increased voluntary exercise.
Inclusion Criteria:
  • Subjects from grades three to five in two school districts in rural Nebraska who had signed informed assent/consents completed by subjects and parents
  • Sub-sample from whom laboratory data was collected; Subjects were only included if they had complete data 
  • Subjects who would benefit from an attenuation in obesity: Subjects with a body fat of at least 22%.
Exclusion Criteria:

Subjects with no signed informed assent/consent, and subjects from the sub-sample with missing data.

Description of Study Protocol:
  • Subjects and parents were required to sign informed assent/consent
  • Major data collection for the fall of 1992 and 1993 took place in August, September and October and for the Spring of 1993 and 1994 in April and May
  •  Lunches were planned with existing kitchen staff over the summer and modifications were installed in the Fall of the first year (Fall of 1992)
  • Nutrition education was delivered in modules using trained, existing classroom teachers
  • Eighteen grade-specific modules (nine per year) were developed by the nutrition research staff in conjunction with the teachers from the intervention school
  • The existing classroom teachers delivered activities designed to promote energy expenditure and decrease time-off-task.
Data Collection Summary:

Dependent Variables Observed difference from pre- to post-intervention

  • Physical fitness: One-mile walk/run time
  • Nutrition knowledge: Grade-specific test designed by nutrition research staff and modified by classroom teacher
  • Spontaneous physical activity: Checklist record of day’s activities performed in 24-hour period prior – transformed into MET level.

A sub-sample of 100 students from both control and intervention schools were recruited for measurements of the following outcome variables:

  • Body composition: Hydrostatic weighing, measured height and weight and percent body fat
  • Classroom physical activity: SOFIT procedure: Trained researchers observed subject’s amount of moment for 10 second periods during physical education class
  • Peak aerobic capacity: Maximal treadmill test
  • Blood chemistry: Measured plasma triglycerides, cholesterol, HDL cholesterol, glucose, insulin, iron and ferritin
  • Blood pressure: Measured systolic blood pressure and diastolic blood pressure
  • Twenty-four-hour energy intake (modified 24-hour diet recall from subject, parents were called to verify response).

Independent Variables

Intervention school: School that received a multi-component program

  1. Nutrition education: Components included basic nutrition, the relationship between diet and general health, nutrition for proper growth and development, healthy food choices, snack alternatives, reducing fat in the diet and food safety
  2. Modified school lunches (using Lunchpower! Program): Reduced energy, fat and sodium lunch which is consistent with the objectives of Healthy People 2000),
  3. Enhanced physical activity: An activity approach which deemphasized team sports and provided exercise and games designed to use large muscle groups for 30 minutes, three times per week.

Control school: No change to existing programs.

Control Variables

Intervention and control subjects were matched for ethnicity, SES and baseline characteristics (grade, height, weight, BMI, mile run).

Statistical Analysis

  • Power analysis was used to determine sample sizes
  • ANOVA to compare the two groups over time.
Description of Actual Data Sample:
  • Original sample: 
    • The total number of subjects included from each school was not reported
    • A sub-sample of students were recruited from each school to collect laboratory data (Control N=236; Intervention N=102)
  • Actual sample:
    • 64 students from control (27% of original sample) and 44 students from the intervention (43% of original sample)
    • Schools were used to collect laboratory data for aerobic capacity, body composition, blood chemistry and physical activity in physical education class
    • Intervention and control subjects were matched on ethnicity, socioeconomic status and baseline characteristics (grade, height, weight, BMI, mile run)
    • Subjects were third, fourth and fifth graders from two school districts
    • 25 control and 11 intervention subjects had at least a 22% body fat; separate analysis was conducted with this sample
  • Withdrawals/Drop-outs: Subjects with incomplete data were excluded
  • Location: Rural Nebraska
  • Race/Ethnicity: 94.3% to 93.6% White
  • SES: 42% and 44% of subjects were eligible for free and reduced priced lunches.
Summary of Results:

Body Weight and Composition

  • No significant differences were found between control and intervention schools at the end of two years for weight, BMI or body fat percent (P<0.05). Note: Percent body fat did not show significant changes; however subjects from both schools showed significant increases in BMI.
  • The nutrition and physical activity interventions had little effect on measures of obesity.

Attenuation in Obesity

  • Among the subjects with body fat of at least 22%, body weight showed similar increases for both control and intervention schools of 8.4±4.1kg and 9.1±3.2kg, respectively
  • Body fat decreased from baseline to the end of year two by 2.7±6.9kg for the control and 2.5±5.9kg for the intervention. These decreases were not significant for within or between school comparisons.
  • BMI showed significant increases for these subjects of 1.4±1.7kg per m2 and 1.4±1.2kg per m2 for control and intervention schools, respectively.
Author Conclusion:

(Author’s words from the discussion)

"The nutrition intervention was successful as judged by the changes in the school lunch program, acceptance of the new lunch program by the students and the nutrition knowledge tests. The physical activity intervention was marginally successful in that only modest changes were evident in the level of physical activity in the classroom. Obesity was unchanged in the intervention school compared to the control school as were all components of metabolic fitness except HDL cholesterol which was greater for the intervention school than the control school. It appears that compensation in both energy intake and physical activity outside of school may be responsible for the lack of differences between the intervention and controls."

Funding Source:
National Livestock and Meat Board
Commodity Group:
University/Hospital: University of Nebraska-Kearney
Reviewer Comments:
  • Did not control analysis for normal growth during this two-year period
  • Authors did not report sample size
  • I question whether this is a true prevention intervention as on page 230 it says “The multi-component approach is recommended for the treatment of obesity…”
  • No explanation was given for why obesity was defined as at least 22% body fat.
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? Yes
  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")? Yes
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%.) No
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  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? No
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? No
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? No
  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? 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? 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? Yes
  6.8. In diagnostic study, were details of test administration and replication sufficient? Yes
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? ???
  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)? No
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? No
  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