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

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

To assess differences through grade eight in diet, physical activity, and related health indicators of students who participated in the CATCH school and family intervention from grades three through five.

Inclusion Criteria:

See Luepker, 1996 for criteria for original cohort.

Exclusion Criteria:

None provided.

Description of Study Protocol:

Ninety-six schools randomized (after baseline measurements complete) to control or intervention; Intervention schools further randomized into two equal subgroups (half receiving family-based program and other half not).


See Luepker, 1996 for details.

  • Student education
  • Moderate to vigorous physical activity (PA) in physical education (PE)
  • Modified school lunch
  • ±Home programs

No intervention during three years of follow-up. Students tracked to within a 100-mile radius of the original CATCH school district.

Statistical Analysis

  • Multivariate repeated-measures analysis (except for dichotomous smoking variable which was analyzed by repeated-measures logistic regression) – including data from grades three through five as available
  • Cases with one more missing values were included
  • Some anomalous data and some plausible but extreme values were deleted to avoid undue influence: Height decrease greater than one cm per grade (eight cases); BMI greater than 50kg per m2 (one case); cholesterol greater than10.35mmol per L (three cases); energy intake greater than 12,000kcals per day (one case), PA greater than10.5 hours per day (99 cases)
  • Limited number of comparisons to primary CATCH hypotheses to control type I error rate from multiple comparisons; expected number of type I errors = 1.05 (0.05 x 21 comparisons)
  • Multiple logistic regression analysis to determine whether likelihood of grade eight participation, given baseline participation, difference by site, sex, ethnicity, intervention group, or baseline end point variables
  • Mixed model, controlling for site, sex, ethnicity, sex X ethnicity interaction, intervention group and other individual level covariates used in repeated measured analysis, used to compare participants’ and non-participants’ baseline levels of end point variables.

Intention to Treat Analysis

All children included in original group regardless of length/degree of intervention exposure.

Data Collection

Blinded measurers since all children left original CATCH schools.

Data Collection Summary:

Dependent Variables

  • Dietary fat, saturated fat and Na: 24-hour recall – grade eight to subsample and CATCH Food Checklist (40 foods/food groups) – grades seven and eight to entire cohort)
  • Moderate to vigorous physical activity (PA): Self-administered PA Checklist at grades six, seven, eight
  • Psychosocial factors: Health Behavior Survey on diet knowledge, diet intentions, social support for PA, smoking behavior at grades six, seven, eight
  • Blood lipids: Total, HDL cholesterol and apolipoprotein B (non-fasting sample in grade eight)
  • Blood pressure: Grade eight
  • Skinfolds: TSF, SSF; grade eight
  • BMI (measured weight, height; grade eight)

Independent Variables

Original CATCH program group (see above).

Control Variables

  • Age
  • Site
  • Gender
  • Ethnicity
  • Intraclass correlation within school and student
  • Gender X ethnicity interaction.
Description of Actual Data Sample:
  • Original sample: 5,106 children, grade three, from original CATCH cohort 
  • Withdrawals/Drop-outs: 34 students (1%) had parental consent for all measures except venipuncture, 286 parents (6%) refused child’s participation and remaining 1,072 students (21%) did not respond, were living beyond a 100-mile radius of a study center or were lost to follow-up
  • Final sample: 3,714 children, grade eight (73% of original cohort), 1,533 children (for 24-hour dietary recall; random sample of original cohort who had completed same in grade three or five; 1,468 used in analysis [some excluded due to extreme or implausible data], from 40 C and 56 I public schools from 12 school districts (equal numbers per study site).
  • Location: San Diego, CA; Houston, TX; New Orleans, LA, Minneapolis, MN
  • Duration: Three school year original intervention (Fall 1991 through Spring 1994) plus three years follow-up without intervention
  • Race/Ethnicity: Original cohort = 69% White, 13% African American, 14% Hispanic
  • SES: Not described.


Summary of Results:


  • Rate not different between intervention and control schools, but some significant differences by demographics and site:
    • Diet recall: Girls greater than boys
    • Risk factor screening/HBS: Whites greater than others
    • All measures: LA and MN greater than CA and TX
    • Non-participants slightly older, greater BMI and skinfolds at baseline.


  • Food checklist

    •  Total fat at grades seven and eight (P=0.003)
    •  Saturated fat at grades seven and eight (P=0.02)
    •  Na at grades seven and eight (P=0.006)
  • 24-hour recall 
    •  Dietary energy at end of three-year intervention (grade five) gone by three-year follow up (grade eight)
    •  Total fat at grade eight (30.6% kcals in I vs. 31.6% in C; P=0.01)
    •  Saturated fat at grade eight (11.3% kcals in I vs. 11.8% in C; P=0.02)
    •  CHO at grade eight (56.6% kcals in I vs. 55.4% in C; P=0.02)
    •  Na at grade eight (3,298mg in I vs. 3,456mg in C; P=0.04)
    • No difference in energy from protein or dietary cholesterol.

Physical Activity

  •  Vigorous physical activity in grade eight (hard breathing most of time while exercise) (30.2 minutes per day in I vs. 22.1 minute per day in C, P=0.001)
  • No difference in total physical activity in grades seven and eight
  • Note:  PA from grades five to eight in both I and C groups.

Anthropometry and Other Physiology

  • No difference in BMI
  • No difference in TSF or SSF
  • No difference in heart rate or blood pressure
  • No difference in blood lipids.

Health Behavior

  •  Healthy food intentions in grade eight (P<0.001)
  •  Healthy food knowledge in grade eight (P<0.001)
  • No difference in positive social support for PA or smoking in grade eight
  • Note:  scores from grades five to eight in I group.


Author Conclusion:
  • The original CATCH results demonstrated that school-level interventions could modify school lunch and school physical education programs as well as influence student behaviors. This three-year follow-up without further intervention suggests that the behavioral changes initiated during the elementary school years persisted to early adolescence for self-reported dietary and physical activity behaviors.
  • The differences between experimental and control students noted in this follow-up, while statistically significant, are narrowing in magnitude over time. If the trends continue, soon no differences will be detectable.
Funding Source:
Government: NHLBI, NIH
NERI-New England Research Institutes
Pharmaceutical/Dietary Supplement Company:
University/Hospital: University of California, University of Minnesota, University of Texas, Tulane University, San Diego State University
Reviewer Comments:


  • Large sample size (CATCH is largest school-based randomized trial ever conducted)
  • Long follow-up time
  • Intention to treat analysis
  • Measurers blind to students’ original intervention group.


  • Did not adjust for maturation
  • Could not follow all changes in sample size
  • No analysis of relationship between behavior change and adiposity.

Other Comments

Although not explicitly stated in the paper, prevention of OB was not a goal of CATCH, but rather aimed to avoid growth inhibition.

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? No
  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) No
  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.) 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%.) 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? Yes
  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? 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? 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)? Yes
  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? No
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