Pediatric Weight Management

Pediatrics and Physical Activity


Trost, SG, Kerr, LM, Ward, DS, & Pate, RR. Physical activity and determinates of physical activity in obese and non-obese children. International J of Obesity 2001;25:822-29.

PubMed ID: 11439296
Study Design:
Cross-Sectional Study
D - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:

The purpose of the study was to compare the physical activity patterns and the hypothesized psychosocial and environmental determinants of PA in an ethnically diverse sample of obese and non-obese middle school children.

Inclusion Criteria:
None Stated
Exclusion Criteria:
Incomplete PA data and missing height and weight
Description of Study Protocol:

Objective measurements wre collected of PA over a 7-day period using the CSA 7164 accelerometer; total daily counts; daily moderate (3-5.9 METs) physical activity (MPA); daily vigorous physical activity (> 6 METs; VPA); and weekly number of 5, 10, and 20 minute bouts of moderate to vigorous PA.


Self-report measures were collected of PA self-efficacy; social influences regarding PA, beliefs about PA outcomes; perceived PA levels of parents and peers; access to sporting and/or fitness equipment at home; involvement in community-based PA organizations; participation in community sports teams; and hours spent watching television or playing video games.

Data Collection Summary:

Independent Variables:  BMI (obese and non-obese)

Dependent Variables:  physical activity, psychosocial and environmental factors

Confounders:  sex, ethnicity

Statistical Analysis:

  • Group differences with respect to age, height, weight, and BMI were tested using independent t-tests.
  • Group differences on the PA and continuous determinant variables were tested using a one-way ANCOVA with sex and race/ethnicity serving as covariates.
Description of Actual Data Sample:

N: 133 non-obese and 54 obese sixth grade children (52.4% female)

Age: mean of 11.4±0.6

Race/Ethnicity: 55.6% African American,

Anthropometrics: Obesity status determined using the age-, race- and gender-specific 95th percentile for BMI from NHANES-1.

Location: USA

Summary of Results:
  • Compared to non-obese children, obese children exhibited significantly lower counts per day (28.3X10±2.01x10 vs 37.7x10±1.41x10; P=0.003); daily participation in MPA (62.6±4.5 vs 78.2±3.2 min/day; P=0.002); and daily participation in VPA (7.1±1.3 vs 13.5±0.9 min/day; P=0.001).
  • Relative to their non-obese counterparts, obese children exhibited significantly fewer 5-min bouts (15.9±1.8 vs 23.4±1.3; P=0.001), 10 min bouts (8.7±1.1 vs 12.6±0.7, P=0.002), and 20 min bouts (3.9±0.6 vs 5.8±0.4, P=0.009) of MVPA over the 7 day monitoring period.
  • Compared to non-obese youth, obese children reported significantly lower levels of PA self-efficacy, were involved in significantly fewer community organizations promoting PA, and were significantly less likely to report their father or male guardian as physically active.
Author Conclusion:
The results are consistent with the hypothesis that physical inactivity is an important contributing factor in the maintenance of childhood obesity. Relative to their non-obese counterparts, obese children exhibited significantly lower daily accumulations of moderate to vigorous PA and participated in significantly fewer continuous 5, 10, and 20 min bouts of moderate-to-vigorous PA. There was also a significant difference between obese and non-obese children with respect to key social-cognitive determinants of youth physical activity behavior.
Funding Source:
University/Hospital: University of Queensland, University of South Carolina, University of North Carolina at Chapel Hill
Reviewer Comments:

Strength:  Use of an objective monitoring device to quantify both the quantity and intensity of PA, 7 days of complete monitoring data in a relatively large sample of free-living children.

Weakness: Cross-sectional nature precluded us from inferring a causal relationship between PA and obesity status, did not conduct sex-specific analyses, did not collect data directly from the parents

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? N/A
  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? N/A
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) N/A
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? N/A
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) N/A
  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")? N/A
4. Was method of handling withdrawals described? Yes
  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%.) 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? N/A
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? N/A
  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? N/A
  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? 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? N/A
  7.6. Were other factors accounted for (measured) that could affect outcomes? N/A
  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? N/A
  8.2. Were correct statistical tests used and assumptions of test not violated? N/A
  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? Yes
  10.2. Was the study free from apparent conflict of interest? Yes