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Haerens L, De Bourdeaudhuij I, Maes L, Vereecken C, Brug J, Deforche B. The effects of a middle-school healthy eating intervention on adolescents' fat and fruit intake and soft drinks consumption. Public Health Nutr. 2007 May; 10 (5): 443-449. PMID: 17411463.

PubMed ID: 17411463
Study Design:
Randomized Controlled Trial
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NEUTRAL: See Research Design and Implementation Criteria Checklist below.
Research Purpose:

To evaluate the effects of a healthy eating promotion intervention in middle schools, combining changes in the school environment with nutrition education through interactive computer-tailored feedback. It was hypothesized that dietary behaviors would be improved in the intervention groups (with and without parental support) compared with the Control Group after nine months of intervention.

Inclusion Criteria:
  • Students in middle schools with technical and vocational education
  • Parental consent was required for their child to complete measurements.
Exclusion Criteria:

None specifically mentioned.

Description of Study Protocol:


A random sample of 15 middle schools out of the 65 schools with technical or vocational training in West Flanders (Belgium) were selected to participate in the study. The 15 schools were randomly assigned to an intervention with parental support (five schools), an intervention without parental support (five schools) or a control group (five schools).

The parents of all seventh and eighth grade students in these schools received an informed consent, in which authorization was required for their child to participate in the study. 


Group randomized controlled trial. 


The school-based intervention was developed to promote healthy food choices and physical activity engagement in order to prevent the increasing prevalence of overweight in children. The intervention was implemented over one school year. Only the healthy food intervention was discussed in this article; the effects of the intervention on anthropometrics and physical activity levels were discussed in another article.

The healthy food intervention was designed by a working group composed of the principal, the physical education teacher or teachers and one or more other teachers. The nutritional intervention focused on three behavioral changes:

  1. Increasing fruit consumption to at least two pieces a day
  2. Reducing soft drink consumption and increasing water consumption
  3. Reducing fat intake.

Strategies were aimed at increasing the availability of healthy food products and decreasing the availability of unhealthy food items at school. To facilitate fruit consumption, fruit was sold once a week at school at low cost or provided free to all seventh and eighth grade students. To increase water consumption and decrease soft drink intake, schools promoted the drinking of water at drinking fountains or at a lower price than soft drinks in vending machines.

Children were provided information about the improved health consequences of eating fruit as opposed to less healthy snacks and drinking water rather than soft drinks. During classes, students received the computer-tailored intervention for fat intake and fruit consumption, which related their intakes to the recommended intakes. Students received tailored feedback about their attitudes, self-efficacy, social support, knowledge, benefits and barriers related to their fruit and fat intake. In addition, teachers were encouraged to organize activities such as healthy breakfast and educational games.

For the intervention with parental support group, a CD with the adult computer-tailored intervention for fat intake was given to parents to use and complete at home. Parents were informed with a brochure that their child used a similar computer-tailored tool at school. They were asked to support their child in making healthy changes suggested in the feedback. 

Statistical Analysis

  • Analysis included descriptive statistics of sample characteristics and linear-mixed models on post-intervention were used to test intervention effects of the school-based healthy diet promotion
  • Post hoc analyses were conducted to determine the direction of differences
  • P-value of <0.05 was considered statistically significant.
Data Collection Summary:

Timing of Measurements

Measures were assessed at baseline (beginning of school year) and at nine months (end of school year). Demographic factors (birth date, gender, occupation of father and mother, number of computers at home) were assessed using a self-administered questionnaire. An estimate of socioeconomic status of the family was obtained by classifying occupations of the father and mother as "white collar" and "blue collar."

Dependent Variables

Three separate self-reported food-frequency questionnaires in the total sample of children:

  • Fat intake and percentage of energy from fat measured using a food-frequency questionnaire
  • Fruit intake measured using a validated food-frequency questionnaire
  • Soft drinks and water intake measured using a food-frequency questionnaire.

Independent Variables

  • Intervention Group with parental support
  • Intervention Group without parental support
  • Control Group. 

Control Variables

  • Gender
  • Baseline values
  • Age and SES
  • Pre and post analyses on percentage of energy from fat were adjusted for pre-post differences in physical activity levels.
Description of Actual Data Sample:

Initial N

  • Total: 2,991 students (37% girls)
  • Intervention with Parental Support Group: 1,226 students (40% girls)
  • Intervention Only Group: 1,006 students (16% girls)
  • Control Group: 759 students (59% girls).

Attrition (Final N)

2,840 girls and boys; 5% of parents did not give permission for their child to participate (N=151 pupils).


11- to 15-year-olds (seventh and eighth graders).


Did not provide information on ethnicity.

Other Relevant Demographics

68% were of lower socioeconomic status (SES).


Although indicated anthropometrics were measured, the results were reported in another article.


West Flanders (Belgium).

Summary of Results:

Key Findings

  • At baseline, an average of 60% of the children exceeded fat intake recommendations and on average, 85% did not meet fruit intake recommendations. Children reported an average three glasses of soft drinks per day.
  • In girls, fat intake and percentage of energy from fat decreased significantly more in the Intervention Group With Parental Support, compared with the Intervention Group Without Parental Support (F>3.9, P<0.05) and the Control Group (F>16.7, P<0.001)
  • In boys, there were no significant decreases in fat intake or percentage of energy from fat as a result of the intervention
  • No intervention effects were found in boys or girls for fruit, soft drinks and water consumption.
Author Conclusion:
  • The intervention was not effective in increasing self-reported fruit and water consumption and no positive effects on soft drink consumption were found for both girls and boys
  • There was a trend for a significant gender interaction effect for fat intake and percentage of energy from fat. For these variables, the intervention was effective in girls, but not in boys. Post-hoc tests revealed that fat intake and percentage of energy from fat decreased significantly more in girls of the Intervention With Parental Support Group, compared with both other groups.
  • The use of school environmental changes to increase the availability of healthy foods in schools, together with the use of computer-tailored feedback to motivate and enable healthy choices in girls and their parents may induce lower fat intake in middle-school girls.


Reviewer Comments:

Strengths of the study included:

  • Clustered randomized design with a high participation rate
  • Combination of a computerized tailored intervention with environmental changes.

Limitations included:

  • Statistics: Incomplete accounting of participants. Initially reported initial N=2,840 (37% girls). However, Table One provides demographics for 2,991 participants. Table Three reports pre- and post-test intake levels for only 33% girls. Furthermore, Table Two pre- and post-intake levels are reported only for 2,395 subjects.
  • The lack of personalized tailored feedback for soft drinks and water consumption could have resulted in an insufficiently intensive intervention for these specific behaviors
  • In regard to gender difference, it is possible that girls were more responsive to the messages of the tailored intervention
  • Self-reported food frequency measurements: Self-reported measures used to assess dietary intakes of adolescents may result in reporting errors
  • Limited data are available to understand the reporting bias in this age group
  • In this study, the effect of the whole school intervention was evaluated; the effects of each component was not assessed
  • Question the generalizability of study to other groups of adolescents
  • Question if time of study was sufficient to assess effects of intervention.

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)
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about?
  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?
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies)
Validity Questions
1. Was the research question clearly stated?
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified?
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated?
  1.3. Were the target population and setting specified?
2. Was the selection of study subjects/patients free from bias?
  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?
  2.2. Were criteria applied equally to all study groups?
  2.3. Were health, demographics, and other characteristics of subjects described?
  2.4. Were the subjects/patients a representative sample of the relevant population?
3. Were study groups comparable?
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT)
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?
  3.3. Were concurrent controls used? (Concurrent preferred over historical controls.)
  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?
  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.)
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")?
4. Was method of handling withdrawals described?
  4.1. Were follow-up methods described and the same for all groups?
  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?
  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?
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?
  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?
  5.5. In diagnostic study, were test results blinded to patient history and other test results?
6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were intervening factors described?
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied?
  6.2. In observational study, were interventions, study settings, and clinicians/provider described?
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect?
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured?
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described?
  6.6. Were extra or unplanned treatments described?
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups?
  6.8. In diagnostic study, were details of test administration and replication sufficient?
7. Were outcomes clearly defined and the measurements valid and reliable?
  7.1. Were primary and secondary endpoints described and relevant to the question?
  7.2. Were nutrition measures appropriate to question and outcomes of concern?
  7.3. Was the period of follow-up long enough for important outcome(s) to occur?
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures?
  7.5. Was the measurement of effect at an appropriate level of precision?
  7.6. Were other factors accounted for (measured) that could affect outcomes?
  7.7. Were the measurements conducted consistently across groups?
8. Was the statistical analysis appropriate for the study design and type of outcome indicators?
  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?
  8.3. Were statistics reported with levels of significance and/or confidence intervals?
  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)?
  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?
  8.7. If negative findings, was a power calculation reported to address type 2 error?
9. Are conclusions supported by results with biases and limitations taken into consideration?
  9.1. Is there a discussion of findings?
  9.2. Are biases and study limitations identified and discussed?
10. Is bias due to study’s funding or sponsorship unlikely?
  10.1. Were sources of funding and investigators’ affiliations described?
  10.2. Was the study free from apparent conflict of interest?

Copyright American Dietetic Association (ADA).