PWM: Eating Behaviors of Children (2006)

Study Design:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:

To determine if eating food away from home (FAH) in childhood is associated with longitudinal change in relative overweight and to determine the tracking between eating FAH from childhood through adolescence.

Inclusion Criteria:

Healthy girls between the ages of eight and 12 years at baseline and 11 and 19 years at follow-up. All participants had a triceps skinfold thickness below the 85th percentile by age and sex at baseline.

Exclusion Criteria:

Participants were included if they provided two complete dietary records, separated by at least one year, with a maximum length of follow-up of 10 years (follow-up time varied because girls exited the study four years after menarche). A dietary record was considered complete if it included at least six days, including one weekend day, and had complete coding of time and place of consumption for all items recorded.

Description of Study Protocol:


  • Participants were a convenience sample of girls originally enrolled in a longitudinal growth and development study started in 1990 at MIT. Girls were recruited from Cambridge and Somerville schools and a MIT-sponsored summer day camp. Participants' friends and siblings were also invited to enroll.


  • Classified food away from home into three categories: Quick-service food, coffeeshop food and restaurant food. For each category, number of occasions per week was counted and a three-category variable was created, representing those who did not eat FAH, those who ate FAH once a week and those who ate FAH twice a week or more. Dietary assessment: Seven consecutive days of dietary records at baseline, at intervals of several years throughout the study (two records separated by at least a year, with maximum length of follow up of 10 years)
  • Height and weight were taken and a BMI z-score calculated to provide a relative measure of adiposity adjusted for age, to minimize the effect of varied time between baseline and follow-up.

Statistical Analysis

  • Analysis of variance adjusted for unbalanced cell size (assess relationship between change in BMI z-score and frequency of eating FAH or percentage of energy derived from eating FAH).
Data Collection Summary:

Timing of Measurements

  • Seven consecutive days of dietary records at baseline and at intervals of several years throughout the study.

Dependent Variables

  • BMI z-scores.

Independent Variables

  • Food eaten away from home and percentage of energy derived from food eaten away from home.

Control Variables

  • Elapsed time between baseline and follow-up; physical activity and age at baseline at follow-up; baseline BMI z-score and ethnicity; parental BMI, income and education.
Description of Actual Data Sample:

  • Initial N: 196
  • Attrition (final N): 101
  • Age: Eight to 12 years at baseline (11 to 19 years at follow-up)
  • Ethnicity: White 74%, Other 26%
  • SES: 40% below $50,000 annually; 60% above $50,000 annually
  • Anthropometrics: All participants had a triceps skinfold thickness below the 85th percentile by age and sex at baseline.
  • Location: Cambridge and Somerville, MA.
Summary of Results:
  • Participants’ baseline BMI z-score was significantly associated with change in BMI z-score and was therefore included in the models.
  • At baseline, 40% of participants considered themselves to be as active as their peers and 51% considered themselves to be more active than their peers.
  • Baseline BMI: Below 85th percentile (96%), above 85th percentile (4%).
  • Follow-up BMI: Below 85th percentile (91%), above 85th percentile (9%).
  • Baseline median age (nine years), follow-up median age (15 years).
  • Baseline FAH (71%), follow-up FAH (86%). Median number of total FAH occasions increased from two to three times a week.
  • Participants who ate quick-service food twice a week or more at baseline had the greatest mean increase in BMI z-score at follow-up and this change was significantly different from that seen in girls who ate quick-service food once a week or not at all (P<0.05).
  • Girls who were eating quick-service food twice a week or more were consuming more energy on average than girls who were eating quick-service food once a week or not at all (303.8 kcal and 212.9 kcal, respectively) but the relationship was not significant (F=2.72, P=0.071)
  • Slight FAH tracking from childhood through adolescence. Modest tracking was observed for those who ate quick-service food (K=0.16, P<0.05) and restaurant food (K=0.15, P=0.055), while no tracking was observed for those who ate coffee-shop food. Few participants ate coffee-shop food at baseline, but this number increased to 25% at follow-up.
Author Conclusion:

Consuming quick-service food appeared to predispose this sample of girls to increase their relative BMI during adolescence. Since approximately 30% of adolescent girls’ meals are eaten away from home and 30% to 32% of these meals are from quick-service food outlets, quick-service meals may be a contributor to rapid weight gain in adolescents.

Funding Source:
Foundation associated with industry:
Reviewer Comments:


  • Controlled for participants’ BMI at baseline.
  • Consistent with previous research on adult women.


  • Limited generalizability (middle and upper class white girls who reported being more physically active than their peers).
  • Possibly misclassified physical activity data (over-reporting).
  • Prospective design would more clearly delineate results.
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? 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) N/A
  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? 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? 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? ???
  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.) ???
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? ???
  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? 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? 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)? ???
  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