Pediatric Weight Management

Child Nutrition and Environment


Ewing R, Brownson RC, Berrigan D. Relationship Between Urban Sprawl and Weight of United States Youth. Am J Prev Med 2006 (Dec); 31 (6): 464-474.

PubMed ID: 1716908
Study Design:
Cross-Sectional Study
D - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:

To analyze the relationship between urban sprawl and BMI changes in adolescents.

Inclusion Criteria:

Data from the 1997 National Longitudinal Study of Youth.

Exclusion Criteria:

Not applicable

Description of Study Protocol:


Not described in this study but may be in the original study reports.



Blinding used

Not applicable


Not applicable

Statistical Analysis

  • Individual- and Household-Level Variables: BMI, household income, highest grade completed by any household member, sociodemographic data, health behaviors, crime levels in the neighborhood, and climate history
  • Place-Level Variables: Linear models were used for BMI. Non-linear models were estimated for overweight, risk of overweight or obesity.
  • Cross-sectional analyses
  • Longitudinal analyses
  • Regression analyses
  • Random intercept models.
Data Collection Summary:

Timing of Measurements

The original study was conducted from 1997 to 2003. This study being reviewed began in 2005 and went into 2006. Cross-sectional analyses were done for a sample in 1997. The same cohort was again assessed in 2002 for a relationship with obesity and urban sprawl in the county where the individual lived. 

Dependent Variable

BMI was measured from self-reported height and weight. CDC growth charts were used to determine percentiles for age and gender.

Independent Variable

Urban sprawl index

Control Variables

Not applicable

Description of Actual Data Sample:
  • Initial N: 8,984
  • Attrition (final N): 7,756
  • Age: Mean age of 14.9 years for each round
  • Ethnicity:
    • 49.3% White
    • 26% Black non-Hispanic
    • 21.2 Hispanic
    • 3.5% other ethnicity
  • Other relevant demographics: 51.2% male
  • Anthropometrics: Mean BMI was 21.9 for each round
  • Location: Researchers were located in Maryland and Missouri, but the location of the study was not described.
Summary of Results:

Key Findings

Study Analyses

BMI County Sprawl

TV Watching

Crime and Climate

First Cross-Sectional Analysis More likely to be overweight or at risk of overweight: Males and blacks. Less likely to be overweight/ risk of overweight: Adolescents with college-educated parents, from higher income households, and those with missing income data. When controlled for individual and household factors, county sprawl had a significant relationship with overweight/risk of overweight (t= -2.30, P=0.022). Children in a more-sprawling area were 1.16 times more likely than in a compact county to be overweight/risk of overweight (95% CI, 1.02-1.31). Positive relationship with TV and overweight/risk of overweight (t=4.50, P<0.001). County sprawl data became more significant with TV watching included in the analysis (t= -2.47, P=0.014) Data were not included in the final model
Second Cross-Sectional Analysis Odds of obesity rose with age, decreased with highest grade completed, and was higher for blacks (compared to whites) and for Hispanics (compared to non-Hispanics)  Statistically significant for obesity when controlled for physical activity, dietary intake, and TV watching. No significance was noted without these three variables.   No significance was noted
First Longitudinal Analysis

BMI rose with age, but at a slower rate of increase. Coefficients for age (positive) and age-squared (negative) were highly significant.
BMI at mean age was higher for males, blacks, and Hispanics, and lower for teens from higher-income families and those with missing income data.

BMI and BMI growth with age were not related to county sprawl    
Second Longitudinal Analysis BMI after relocating was strongly associated with BMI before the move. BMI after relocation had significant association with changes in age between interview rounds (t=3.03, P=0.003).  Difference in level of sprawl across counties was not statistically significant. Lack of significance may be from few relocations and that BMI changes were small for individuals (SD =0.59).    

Other Findings

  • The cross-sectional analyses found that teens in sprawling areas were more likely to be overweight/at risk for overweight
  • Young adults in sprawling areas were more likely to be obese
  • Stronger relationships were observed between sprawl and BMI >25 when TV watching and exercise were considered
  • Longitudinal analyses showed no significant associations between sprawl and changes in weight.
Author Conclusion:

Urban sprawl neither does nor does not cause obesity in any population cohort.

Funding Source:
Government: National Cancer Institute, National Institutes of Health
Reviewer Comments:
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) ???
  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? N/A
  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? N/A
  2.3. Were health, demographics, and other characteristics of subjects described? N/A
  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? ???
  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? ???
  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? 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? N/A
  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? 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? ???
  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)? 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? 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