Pediatric Weight Management

Pediatrics and Physical Activity


Crespo CJ, Smit E, Troiano RP, Bartlett SJ, Macera CA, Andersen RE. Television watching, energy intake, and obesity in US children. Arch Pediatric Adolescent Medicine 2001;155:360-65.

PubMed ID: 11231802
Study Design:
Cross-Sectional Study
D - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:
To examine the relationship between television watching, energy intake, physical activity and obesity status in US boys and girls aged 8 to 16 years.
Inclusion Criteria:
Not specified
Exclusion Criteria:

Children who had a proxy answer to the physical activity and television questions in the mobile examination center were excluded from the analyses.

Description of Study Protocol:

Data were from the NHANES III, home interviews and detailed clinical examination in the mobile examination center were conducted.

Data Collection Summary:


  • Physical activity categories (1 or less times per week to 8 or more times per week)
  • Television viewing (recall based in the average of 2 recalls – categorized from 1 hour or less, 2 hours, 3 hours, 4 hours, and 5 or more hours per day)

Dependent: Obesity (BMI)

Statistical Analyses:

  • Descriptive statistics include prevalences, Standard Errors and 95% confidence intervals. 
  • Logistic regression using Proc RLogist was used to calculate estimated relative risk and the 95% CI using both television viewing (hours / day) and physical activity levels (times / week)
Description of Actual Data Sample:

4069 children, aged 8 to 16. This sample is nationally representative.

Summary of Results:
  • No consistent association between prevalence of obesity and weekly bouts of vigorous PA were found.
  • The prevalence of obesity increased as hours of television watching increased (p<.05)
  • After adjusting for age, BMI, race/ethnicity, family income and weekly bouts of physical activity, TV viewing was positively associated with energy intake. The effect was stronger among girls (R =.43) than among boys (R = .26).
  • After adjusting for age, BMI, race/ethnicity, family income, energy intake, physical activity), higher TV viewing was significantly associated with greater risk of obesity among girls. RR ranged from 2.5 to 3.9 for 3-5 hours of TV compared to rates for people watching 1 hour.
  • The relative risks were greater than 1.0 for males but not statistically significant.


Author Conclusion:
  • There were no consistent associations between the prevalence of obesity and weekly bouts of vigorous physical activity.
  • The inability to see associations with activity may be due to the lack of sensitivity of the NHANES III questionnaire to accurately measure physical activity in children.
  • Increased television watching was associated with a higher prevalence of obesity among girls, but not among boys. Children who watched the most number of hours of television a day had the highest prevalence of obesity: this held true after controlling for age, race/ethnicity, and family income.


Overall conclusion:

  • The prevalence of obesity is lowest among children watching 1 or fewer hours of television a day and highest among those watching 4 or more hours of television per day.
  • Television watching was positively associated with obesity among girls even after controlling for age, race/ethnicity, family income, weekly physical activity and energy intake.
Funding Source:
University/Hospital: John Hopkins School of Medicine
Reviewer Comments:

Strengths: A large, representative sample



  • Both PA and television viewing were assessed by self-report and the question still remains how well they can be assessed by self-report.
  • They were also assessed by a single item.
  • The study only assessed TV viewing and does not address other forms of inactivity.
  • It is a cross-sectional study.
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? No
  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? N/A
  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.) 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? 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? 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? 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? N/A
  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? 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? N/A
  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? N/A
  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? No
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  7.7. Were the measurements conducted consistently across groups? N/A
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)? 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? 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? N/A
  9.2. Are biases and study limitations identified and discussed? N/A
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