Pediatric Weight Management

PWM: Environment (2012)

Citation:

Crawford DA, Timperio AF, Salmon JA, Baur L, Giles-Corti B, Roberts RJ, Jackson ML, Andrianopoulos N, Ball K. Neighbourhood fast food outlets and obesity in children and adults: The CLAN study. Int J Ped Obesity. 2008: 3; 249-256.

PubMed ID: 18608630
 
Study Design:
Cross-Sectional Study
Class:
D - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:

To examine associations between density of and proximity to fast food outlets and weight in a sample of children and their parents.

Inclusion Criteria:
  • Participants in the CLAN (Children Living in Active Neighbourhoods) study in 2004
  • Eight- to nine-year-old and 13- to 15-year-old children
  • Children and their parents who had available data on height and weight in 2004 and who lived at the same residential address for the previous three years.
Exclusion Criteria:

None listed.

Description of Study Protocol:

Recruitment

  • The families in the CLAN study were originally recruited from 19 state elementary schools in Melbourne, Australia in 2001
  • Schools were selected using stratified random sampling proportionate to school size, based on the Socioeconomic Indices for Areas
  • All students and their parents within the preparatory grade (primary school entry-level) and grades five and six in participating schools were invited to take part in the 2001 data collection.

Design

Cross-sectional.

 Statistical Analysis

  • Descriptive statistics were used to examine demographic characteristics of the sample, children's BMI z-scores and parent's BMI, prevalence of overweight and obesity among children and parents, and the three fast food outlet measures
  • For children, separate bivariate linear regression analyses were performed within age and sex groups to examine associations between each of the independent variables (presence of any fast food outlets, fast food outlet density; distance to the nearest fast food outlet) and BMI z-score
  • In addition, each independent variable was entered into separate bivariate logistic regression analyses to predict the odds of being overweight or obese. These analyses were repeated for mothers and for fathers.
  • All analyses were performed in Stata 8.0
  • Logistic and linear regression analyses adjusted for physical activity and for clustering of participants according to the school attended by the child at baseline (the sampling unit) using the cluster command. 
Data Collection Summary:

Timing of Measurements

  • The CLAN study started in 2001
  • A follow-up was conducted in 2004 and data from this follow-up was used.

Dependent Variables

  • Childs' weight status: Calculated from measured height and weight (taken privately in light clothing without shoes at the child's school using digital scales and a portable stadiometer). International age- and sex-specific cut points were applied to body mass index (BMI=kg/m2) to define overweight/obesity. BMI z-scores were also calculated based on the US reference population.
  • Parents' weight status: One parent was asked to complete a questionnaire in which they reported their own height and weight and that of their spouse/partner. Body mass index was calculated (BMI=weight [kg]/height [m2]). Parents were classified as not overweight (BMI less than 25), overweight (BMI 25 or more and less than 30) or obese (BMI 30 or more). For the purpose of analyses, parents classified as overweight and those classified as obese were combined.
  • Child's physical activity: Each child was asked to wear a Manufacturing and Technology, Inc. accelerometer (Model AM7164-2.2C) for eight days to provide an objective estimate of their overall physical activity. Age-specific regression equations were applied to the data to compute the total time children spent in moderate-to-vigorous physical activity (MVPA, three METS or more) on each day. For each child, mean duration of MVPA per day was calculated using data from at least four days on which accelerometer counts totaled between 10,000 and 20 million counts and total duration of vigorous-intensity physical activity (METS or more) totaled less than six hours, and excluding the first and last days of monitoring.
  • Parents' physical activity: One parent reported the total duration they and their partner (respectively) usually spent doing moderate-intensity physical activity (for at least 10 minutes continuously; including walking) and vigorous physical activity (that made them "breathe harder or puff and pant') in a week. These data were truncated consistent with instructions from the Active Australia Survey on which the items were based and the total duration of physical activity per week was computed separately for mothers and fathers. The validity and reliability of the original instrument has been shown to be acceptable.

Independent Variables

  • Neighborhood fast food outlets: In 2004, the street addresses of fast food outlets within the neighborhood (and surrounding neighborhoods) in which participants resided were identified using on-line telephone directories and company Web sites. For the purposes of this study, eight common fast food chains or franchises from which ready-to-eat meals could be purchased without table service were included: McDonalds, Red Rooster, KFC, Hungry Jacks, Subway, Nando's, Pizza Hut and Pizza Haven. Objective measures of access to fast food outlets were determined in 2005 using the Geographic Information Systems (GIS) software package Arc-View 3.3 and spatial data supplied by the State Government of Victoria. Within the GIS, circular buffers of 2km radius were created around each residential point and the number of fast food outlets (points) was counted within each buffer.
  • Three measures of access to fast food outlets were created based on residential location:
    • Whether there were any fast food outlets within a 2km radius of participants' homes
    • Density (number) of fast food outlets within a 2km radius
    • Distance (km) via the road network to the nearest fast food outlet (regardless of the buffer).

Control Variables

  • Physical activity
  • Clustering of participants according to the school attended by the child at baseline (the sampling unit) using the cluster command. 
Description of Actual Data Sample:
  • Initial N:
    • 140 preparatory grade
    • 269 in grades five and six
    • 343 fathers
    • 389 mothers
  • Attrition (final N):
    • Eight- to nine-year-old children: 72 boys, 65 girls
    • 13- to 15-year-old children: 111 boys, 132 girls
    • 322 fathers
    • 362 mothers
  • Age: Children, eight to nine years or 13 to 15 years; no information on age of parents
  • Other relevant demographics:
    • 86% of respondents were married or living together
    • 47% of mothers and 41% of fathers were tertiary educated
    • 24% of mothers and 15% fathers had completed high school
    • 8% of mothers and 25% of fathers had a technical or trade qualification
    • 22% of mothers and 10% of fathers had not completed high school
  • Anthropometrics: Shown in results
  • Location: Melbourne, Australia.
Summary of Results:

 Key Findings

  • 26% of the younger boys and girls, 32% of the older boys and 27% of the older girls were classified as overweight or obese
  • Among the adults, 63% of fathers and 38% of mothers were overweight or obese. Except for the mothers, the prevalence of overweight and obesity in the study sample compares favorably with the most recent population data.
  • Overall, there were no baseline differences in weight status between those included in the analysis and those who were excluded or not followed up
  • 81% of study participants had a fast food outlet within 2km of their home. The mean density of fast food outlets within 2km was 3.9 (SD=2.8; range zero to 15); the mean distance to the nearest fast food outlet was 2.1km (SD=2.1; range 0.1 to 16.6km).
  • On average, older girls lived closer to a fast food outlet than younger girls (2.1±1.8 vs. 2.8±3.4, p<0.05)
  • Among older boys and girls, those with at least one fast food outlet within 2km of their home had lower BMI z-scores
  • Among adult males, the further they lived from a fast food outlet, the higher their BMI
  • Among older girls, the likelihood of being overweight or obese was reduced by 81% if they had one or more fast food outlet within 2km of their residential address, and by 14% with each additional outlet within 2km
  • Among adult males, the likelihood of being overweight or obese was reduced by 50% if they had one or more fast food outlet within 2km of their residential address, and increased by 13% for each additional kilometer to the nearest food outlet. 

 Weight Status and Body Mass Index (BMI) Among Children and Parents

  Eight- to Nine-year-old Children 13- to 15-year-old Children Parents
 

Boys

(N=72)

Girls

(N=65)

Boys

(N=111)

Girls

(N=132)

Fathers

(N=322)

Mothers

(N=362)

Weight status       
Overweight (%) 19.4  18.5  25.2  22.7  47.2  25.1 
Obese (%) 6.9  7.5  7.2  4.6  16.2  12.7 
BMI (mean, SD)b   0.48 (0.96) 0.51 (0.86)  0.47 (0.97)  0.45 (0.82)  26.4 (3.7)  24.7 (4.5) 

aFor children, overweight and obesity were defined using international age and sex-specific cut-points; for parents, overweight was defined as 25 or more and less than 30, and obesity was defined as BMI 30 or more.

bFor children, BMI refers to BMI z-score.

Other Findings

A higher proportion of mothers (44% vs. 31%, P<0.001) and fathers (40% vs. 30%, P<0.01) who were included in the analyses were tertiary educated compared with those who were excluded or not followed up, and a greater proportion of those included in the analyses were also married or in a defacto relationship (88% vs. 79%, P<0.01).

Author Conclusion:

While consumption of fast food has been shown to be associated with obesity, this study provides little support for the concept that exposure to fast food outlets in the local neighborhood increases risk of obesity.

Funding Source:
Government: Australian National Health and Medical Research Council
Other:
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) N/A
  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) 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? N/A
  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? ???
3. Were study groups comparable? N/A
  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? 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? ???
  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%.) ???
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? No
  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? Yes
  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? 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)? 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