PWM: Physical Activity and Inactivity (2006)

Study Design:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
To assess the effects of reducing television, videotape, and video game use on changes in adiposity, physical activity, and dietary intake.
Inclusion Criteria:
All third- and fourth-grade students in 2 public elementary schools in a single school district in San Jose, Ca were eligible to participate.
Exclusion Criteria:
See inclusion criteria above.
Description of Study Protocol:

The intervention incorporated 18 lessons of 30-50 minutes into the standard curriculum that was taught by the regular third- and fourth-grade classroom teachers. Newsletters that were designed to motivate parents to help their children stay within their time budgets and that suggested strategies for limiting television, videotape & video game use for the entire family were also distributed to the parents. To help with budgeting, each household also received an electronic television time manager. Duration: 1 academic year.

Data Collection Summary:


  • BMI (measure weight & height)
  • Triceps skinfold thickness (measured)
  • Waist and hip circumference – wait-to-hip ration (measured)
  • Time children spent watching television, watching movies or videos on a VCR & playing video games (child-report & parent-report)
  • Overall household television viewing (parent’s report)
  • Amount of time the child spent in other sedentary behaviors (child & parent report)
  • Physical activity (child report of previous day’s out-of-school physical activities)
  • Dietary intake: High-fat foods (1-d FF recall)
  • Children also reported how often they ate breakfast and dinner in a room with the television turned on
  • Cardiorespiratory fitness (20-m shuttle run test)


Intervention school or Control school.

Control Variables

Schools were sociodemographically and scholastically matched by district personnel.

Statistical Analysis

A mixed model analysis of covariance approach was used.

Description of Actual Data Sample:

N: 92 (86.8%) of 106 eligible children in the intervention school and 100 (82.6%) of the 121 eligible children in the control school participated in baseline and post-intervention assessments.

Location: San Jose, CA

Race/Ethnicity: not reported

SES: Schools were matched by sociodemographic variables.

Summary of Results:

As expected for children of this age, BMI, triceps skinfold thickness, waist circumference, and hip circumference all increased in both intervention and control children during the course of the school year.

Effects on Adiposity

Compared with controls, children in the intervention group had statistically significant relative decreases in BMI, triceps skinfold thickness, waist circumference, an waist-to-hip ratio.

Effects on Media Use, Diet & Physical Activity

The intervention significantly decreased children’s television viewing, compared with controls, according to both child and parent reports (relative reductions of about 1/3 from baseline).

The intervention significantly reduced the frequency of children eating meals in a room with a television turned on.

Intervention group children also reported relative reductions in servings of high-fat foods compared with controls, although these differences were not statistically significant.

There were no significant intervention effects on reports of children’s physical activity levels or performances (physical fitness).

Author Conclusion:
Reducing television, videotape, and video game use may be a promising, population-based approach to prevent childhood obesity.
Funding Source:
Government: NHLBI
Foundation associated with industry:
Reviewer Comments:

Assessments were performed by trained staff, blinded to the experimental design at baseline and after the completion of the intervention.

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? 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? Yes
  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.) N/A
  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? N/A
  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? 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? No
  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? N/A
  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? N/A
  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)? N/A
  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? Yes
  10.1. Were sources of funding and investigators' affiliations described? N/A
  10.2. Was the study free from apparent conflict of interest? N/A