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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 determine the relationship of juvenile obesity to dietary fat, particularly saturated fat and with dietary energy (controlling for activity patterns). 

Hypothesis:  Obese children consume a diet higher in fat than normal-weight children and this correlates with their obesity more than dietary energy, when one controls for activity levels.

Inclusion Criteria:
  • Obese: BMI more than 95th percent of the reference values for age and sex (Hammer, 1991)
  • Non-obese: BMI less than 75th percent of the reference values for age and sex.
Exclusion Criteria:

Children and adolescents with eating disorders, including dieting, genetic disorders of obesity, physical limitations, other co-morbid conditions, or treated by medications that could affect eating or physical activity.

Description of Study Protocol:
  • Obese group were patients of the Children’s Exercise and Nutrition Center which is a clinic that uses an inter-disciplinary behavior modification approach to the treatment of juvenile obesity. These subjects were on the waiting list for treatment.
  • Non-obese subjects were recruited from community advertisements
  • Obese and non-obese were recruited equally throughout the year to control for seasonal variation in food
  • Before the start of the study, subjects were given information regarding a general overview of obesity such as the risks associated with obesity/prevalence, etc. They were instructed on the importance of accuracy of dietary and activity recall in order to receive the best treatment.
Data Collection Summary:
  • Dependent variables: 
    • BMI
    • % BMI: Actual BMI/median BMI for age and sex (height and weight measured following stand protocol)
    • Body fat: Bioelectrical Impedance Analysis
  • Independent variables: 
    • Total energy
    • Macronutrient intake: Sugar, total fat intake and saturated fatty acid intake (Diet history interview included 24-hour recall of usual dietary intake, modified food frequency questionnaire (FFQ) and questions to verify intake
    • Activity patterns (activity interview)
  • Control variables: 
    • Gender and age
    • Non-obese subjects were recruited by stratifying age, gender and socioeconomic background
  • Statistical analysis: Linear regression.
Description of Actual Data Sample:
  • Original sample: 195 children and adolescents age four to 16 years participated in this cohort 
  • Withdrawals/Drop-outs: 11 excluded from analysis because their BMI was between 75th and 94th percentile and three excluded for symptoms of disordered eating
  • Final sample: 181 children divided into two groups:
    • Obese (BMI greater than 95th percentile for age and sex) 40 males and 51 females
    • Non-obese (BMI less than 75th percentile for age an sex) 35 males and 55 females
  • Race/Ethnicity: Not specified
  • SES: Majority middle-class families
  • Age:  Four to 16 years old
  • Location: Ontario, Canada.
Summary of Results:

There were no significant differences in age or income between two groups. 

  • Dietary intake:
    • The obese subjects consumed sig. more total calories, total fat in grams and saturated fatty acids in grams than did the non-obese subjects
    • They also consumed sig. more energy, fat and SFA as a percentage of goal (their need) for age and sex
    • When the energy and fat intake were expressed per kg body weight and per kg lean body mass, the obese consumed less than the non-obese subjects
  • Fat as perent of energy: There was no difference in fat as a percentage of energy between the two groups
  • Sugar: The obese subjects consumed significantly more sugar (167±60g) than did the non-obese subjects (134±46g)
  • Step-wise multiple regression: Based on step-wise multiple regression, the total energy consumed, not total fat or SFA, had the strongest relationship to the subject’s percentage body fat, controlling for activity levels.
Author Conclusion:

Future education for obesity prevention and treatment should focus on the total calories consumed and expended in activity and shift the focus merely from dietary fat.

Funding Source:
University/Hospital: Hamilton Health Sciences Corporation (Canada)
Reviewer Comments:
  • It has been shown that children and adolescents do not have the ability to accurately report portion sizes, so the lack of parent in the interview could have given inaccurate results
  • Obese subjects may have under-reported in order to receive help for their health problems
  • Stage of obesity differed between subjects
  • Cross-sectional study does not reveal etiology of obesity
  • Large sample size.
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.) Yes
  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? Yes
  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? Yes
  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? No
  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)? Yes
  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