Increase Font Size Decrease Font Size View as PDF Print
Citation:
Horne PJ, Tapper K, Lowe CF, Hardman CA, Jackson MC, Woolner J. Increasing children's fruit and vegetable consumption: A peer-modelling and rewards-based intervention. Eur J Clin Nutr. 2004 Dec; 58(12): 1,649-1,660.

PubMed ID: 15252421
Study Design:
Cluster Randomized Trial
Class:
A - Click here for explanation of classification scheme.
POSITIVE: See Research Design and Implementation Criteria Checklist below.
Research Purpose:

To determine the effects of a peer-modeling and rewards based intervention on the consumption of fruits and vegetables in school children.

Inclusion Criteria:
  • Age five to 11 years old
  • London inner-city Schools (Brixton and Stockwell)
  • Schools were selected by local health promotion unit or education authority.
Exclusion Criteria:

Not described.

Description of Study Protocol:

Recruitment

  • Schools were chosen by the local health promotion unit or education authority
  • All children in the schools were involved
  • It is unclear if a child could choose not to participate.

Design

Group randomized controlled trial:

  • 12-day baseline period (fruits and vegetables introduced at mid-morning snack and lunch)
  • 16-day intervention period (fruits and vegetables presented at mid-morning snack and lunch plus peer modelling and rewards)
  • Four-month maintenance phase.

Intervention

  • Baseline (12 days):
    • At lunch, children who received school lunch were given a whole fruit or a cooked vegetable in a fixed cycle: 60g portions of a cooked vegetable or 80g of a raw fruit
    • Fruits used were apples, pears, bananas and satsumas. Vegetables used were peas, carrots, sweet corn and broccoli
    • Children who brought lunch from home could select either a fruit or vegetable
  • Intervention (16 days):
    • Peer modelling videos were used (featuring "Food-Dudes" battling the evil "Junk-Punks" and letters from the Food-Dudes were read on at least two out of three days (six different episodes)
    • Rewards such as Food-Dudes stickers, pens, pencil cases, rulers and erasers were used (small reward if they tried or ate part of their serving; more substantial reward if they ate all of the serving)
    • Home snack packs encouraging children to eat fruit and vegetables at home and at school were used to engage parents; these were delivered to parents by their children, included suggestions of how to meet the five-a-day target at home as well as a sticker card and stickers to mark progress.
  • Maintenance (four months):
    • No Food Dude videos and school staff were asked to read out just one Food Dude letter at the start of each week 
    • Wall charts were introduced to enable rewards and illustrate progress (five charts, two weeks each)
    • The second home snack packs were delivered to parents
    • Measurements were taken the last eight days. 

Statistical Analysis

  • Cohen's κ coefficient was used to assess agreement between weighed and rated measures (to reconcile visual estimates with weighed measurements; 10% of measures were validated with this method)
  • Post-hoc T-tests used for assessing consumption compared between baseline and intervention
  • Two three-way mixed analysis of variance tests were conducted for analyzing the home data
  • Four-way mixed analysis of variance was used to analyze liking scores
  • Six post-hoc T-tests were used to test for difference between baseline and intervention liking for fruit and vegetables.
Data Collection Summary:

Timing of Measurements

Measures were taken at initial and final baseline (B1 and B2) and at initial and final during intervention (A and B) and follow-up (C).

  • If there was just one presentation of each food at baseline, only one baseline mean was calculated
  • If a child had missing data (i.e., they were absent), that measure was excluded from the calculation of mean consumption.

Dependent Variables

  • The amount consumed of each portion of fruit and vegetable was visually estimated and rated on a five-point scale by independent raters (10% of the observations were validated against actual weight of food consumed)
  • Home consumption was measured by a parental 24-hour food recall of all foods consumed:
    • Only a sub-sample was interviewed
    • Parents were phoned daily by a researcher
    • Parents used food diaries as an aid
    • Intervention measurements were taken the last eight days of the intervention phase.

Independent Variables

Participation in peer modeling and rewards-based intervention.

Description of Actual Data Sample:
  • Initial N: 749 children
  • Attrition (final N): Not reported, assumed 749 children
  • Age: 6 to 11 years
  • Ethnicity: Predominantly Caucasian, smaller proportion from ethnic minorities
  • Location: Two inner-city schools in London; deprivation level below the national average. 
    • Brixton, North Wales (364 students, aged 5 to 11 years, 45 sub-sample)
    • Stockwell, North Wales (385 students, aged 5 to 11 years, 39 sub-sample).
Summary of Results:

Key Findings

  • Following analysis of lunchtime fruit consumption, averaged across children of all ages in both schools, using a four-way mixed ANOVA and post hoc T-tests:
    • There were significant interactions between school and study phase, F(2,700) = 233.41, P<0.001; school, study phase and food, F(2, 700) = 5.88, P<0.005; and school, study phase, food and age, F(2, 700) = 3.46, P<0.05
    • Post-hoc tests showed that, for the experimental school, in all instances (i.e., for fruit and vegetable consumption by both five- to seven- and seven- to 11-year-olds), consumption was significantly higher at intervention compared to baseline. In all instances, consumption was also significantly higher at follow-up compared to baseline.
    • Further comparisons showed significant declines between intervention and follow-up for fruit consumption by both age groups and for vegetable consumption by seven- to 11-year-olds
    • Vegetable consumption by five- to seven-year-olds; however, showed no decline between intervention and follow-up
    • In the control school, vegetable consumption was significantly lower at baseline two compared to baseline one and findings were consistent across both age groups
    • Fruit consumption showed no change across the three study phases for five- to seven-year-olds, but showed significant declines between baseline one and follow-up and between baseline two and follow-up for seven- to 11-year-olds
  • Additional analyses were conducted on the lunchtime data in order to determine the way in which overall consumption means were constituted, specifically, whether in baseline there were children who ate little, a moderate amount, or a great deal of the fruit and vegetables presented, and the way in which consumption in these different groups was affected by the intervention. The results showed that:
    • A large proportion of children were consuming less than 20% of the foods provided to them at baseline; 38% and 26% of children for fruit and vegetables, respectively, in the experimental school, 63% and 47%, respectively, in the control school
    • In contrast, only a small proportion of children were consuming over 80% of these foods; 14% and 11% of children for fruit and vegetables, respectively, in the experimental school; 3% and 9%, respectively, in the control school
    • Children in each of these subsets showed changes in consumption of fruit and vegetables at lunchtime during the course of the study as follows:
      • In the experimental school, those children who ate the least during baseline (0% to 19%) showed the largest increases in consumption during intervention and at follow-up; from 4% (baseline) to 68% (intervention) and 48% (follow-up) for fruit and from 11% (baseline) to 48% (intervention) and 43% (follow-up) for vegetables. Those children who ate the most at baseline (80% to 100%) consumed 94% fruit in baseline, 92% in the intervention and 76% at follow-up; for vegetables it was 93% (baseline), 90% (intervention) and 89% (follow-up).
      • In the control school, those children who ate the least during baseline showed little change during the course of the study; from 2% (baseline one) to 7% (baseline two) and 5% (follow-up) for fruit, and from 7% (baseline one) to 4% (baseline two) and 7% (follow-up) for vegetables
    • By contrast, the consumption of those who ate the most during baseline went from 90% (baseline one) to 47% (baseline two) and 13% (baseline three) for fruit, and from 92% (baseline one) to 64% (baseline two) and 55% (baseline three) for vegetables
    • There were also significant increases in fruit and vegetable consumption at home (P<0.05).
Author Conclusion:

The intervention was effective in bringing about substantial increases in children's consumption of fruit and vegetables.

Reviewer Comments:

Limitations:

  • Limited to four types or fruit and four types of vegetables
  • Rewards were given to class, not individual children. Rewards tend to have detrimental effect on food preferences if they not highly desirable.
  • During maintenance phase not all procedures were followed per teacher self-report. This was due to no procedures or incentives to keep the program going.

Research Design and Implementation 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)
Yes
  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 nutrition or dietetics practice?
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?
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)
Yes
  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 used? (Concurrent preferred over historical controls.)
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?
N/A
  3.5. If case control or cross-sectional 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. Criterion may not be applicable in some cross-sectional studies.)
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?
???
  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?
No
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate?
No
  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.)
No
  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?
Yes
  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?
Yes
  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)?
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
 
 

Copyright American Dietetic Association (ADA).