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PWM: Foods and Nutrients (2006)

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

To analyze the association between nutritional and familial factors and obesity in boys and girls.

Inclusion Criteria:

Children ages six to 12 years from Province de Luxembourge, Belgium.

Exclusion Criteria:

Not specified.

Description of Study Protocol:

School classes with children at the ages six to eight, eight to 10 and 10 to12 years were selected by a randomization procedure, taking into consideration the different school systems in Belgium consisting of communal, state and private schools. This was done to avoid selection bias in socioeconomic variables.

Data Collection Summary:
  • Dependent variables:
    • BMI (measured height and weight following standardized protocols)
    • Waist to hip ratio (WHR)
  • Independent variables:  
    • Three-day food record completed by children with assistance of teachers and parents
    • Familial aggregation of disease, lifestyle, physical activity, demographic data, birth data, social and familial conditions (questionnaire)
  • Control variables: Age and gender
  • Statistical analysis: ANOVA and multiple regression analysis.
Description of Actual Data Sample:
  • Original sample: 1,028 boys and girls agreed to participate 
  • Withdrawals/Drop-outs: Children with missing data
  • Final sample: 955 children
  • Location: Province de Luxembourge, Belgium
  • Race/Ethnicity: Predominantly Belgium citizens
  • SES: Rural area – SES not directly specified. Authors indicated the families were in a rural environment with mean incomes below other parts of Belgium and the parents had educational levels below the standard for Belgium. 
  • Age: Six to 12 years (Age strata: Six to eight, eight to 10 and 10 to 12 years).
Summary of Results:

Boys

  • No significant relationship was found between anthropometric data and total energy intake
  • Boys tended to have a higher total energy intake than girls Intake of protein and cholesterol was significantly higher in eight to 10 year old boys compared with girls at the same age
  • Fat, in both absolute terms and as a grams per kcal, showed a positive significant correlation with BMI. When expressed as grams per kcal the correlation was also significant with skinfolds.
  • Carbohydrate intake showed negative, significant relationships to BMI (both in absolute amounts and when expressed as grams per kcal). Grams per kcal CHO also showed significant negative association with skinfolds.
  • Fiber intake showed no significant correlation
  • Protein intake when expressed as grams per kcal showed a positive, significant association with BMI, but not when it was expressed in absolute terms. 

Girls

  • No fully significant correlations were found for the same analyses in girls
  • The WHR showed no significant relationships to the energy intake or its macronutrient components, neither in the total sample, nor in the gender or age groups, suggesting that this ratio is regulated by other nutritional factors in these children.
Author Conclusion:

The lack of correlation between factors indicating obesity and total energy intake suggests that the positive energy balance causing obesity is due mainly to a low energy output. However, since energy intake measures are so imprecise, overeating cannot be excluded, particularly since elevated consumption of food with high contents of fat found in these children seems to be poorly regulated.

Funding Source:
Government: National Center for Research in Nutrition and Health
University/Hospital: University of Goteborg (Sweden), Catholic University of Louvain (Belgium)
Reviewer Comments:
  • Strengths: Large sample
  • Weaknesses: Rural area of Belgium, may not be generalizable to other areas of Belgium, much less generalizable to other areas of the world.
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) 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 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? 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 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? ???
  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? 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? No
  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? 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