Pediatric Weight Management

PWM: Physical Activity and Inactivity of Youth (2006)

Citation:

Obarzanek E, Schreiber GB, et al. Energy intake and physical activity in relation to indexes of body fat: National heart, lung, and blood institute growth and health study. American Journal of Clinical Nutrition 1994; 60: 15-22.

PubMed ID: 8017331
 
Study Design:
Cross-Sectional Study
Class:
D - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:

To examine the relationship between obesity, energy intake & physical activity in a large cohort of black & white girls.

Inclusion Criteria:
  • Black or white girls, within 2 weeks of age 9 or 10 years at the time of the first clinic visit,
  • Parents of guardians who identified themselves as being of the same race as she was and
  • Her parents or guardians completed a household demographic information form and gave informed consent.
Exclusion Criteria:
Description of Study Protocol:

Berkeley & Cincinnati sites recruited participants from public & parochial schools that were racially & socioeconmically diverse. Westat recruited participants primarily from the Group Health Association membership listing of families who had girls ages 9-10 years.

Data Collection Summary:

Dependent:  BMI (height & weight measured following standardized protocol) & Sum of 3 skinfold-thickness measurements.

Independent:  

  • Total energy intake, total fat intake & % of energy from total fat & saturated fatty acids (consecutive 3-day food records), Physical activity (3-day physical activity diaries & Physical activity patterns questionnaires), Sedentary activity (assessment of # of hours of television & video watched);
  • Income (questionnaire) & Level of education (questionnaire).

Control Variables:  Race/ethnicity, Age, Income & Level of education.

Statistical Analysis:  Multivariate regression analyses analysis.

Description of Actual Data Sample:

Original Sample:  2379 black & white girls (1166 white, 1213 black).

Final Sample:  2147 girls (1044 black, 1103 white)

Location:  3 field centers (Berkeley, CA, Cincinnati, OH & Rockville, MD).

Race/Ethnicity:  Black & white girls.

SES: diverse population.

Age:  9-10 y.

Summary of Results:
  • BMI & skinfold thickness were highly correlated in this study (r=0.89).
  • Compared with white girls, black girls had higher intakes of energy, grams of total fat, & % of energy from total fat. However, black girls had slightly lower intakes of % of energy from saturated fatty acids.
  • Multivariate-regression analyses showed that age, number of hours of television & video watched, percent of energy from saturated fatty acids & the activity patterns score best explained the variation in BMI & sum of 3 skinfold-thickness measurements for black girls (R2 for this model – BMI as outcome - was 0.04 (P<0.0001).
  • The best model for white girls included age, # of hours of television & video watched & percent of energy from total fat (R2 for this model – BMI as outcome - was 0.05 (P<0.0001).
  • (BMI) For both races, total energy intake, total grams of fat intake & the activity diary scores were not found to be significantly & independently related to BMI.
  • (Skinfold thickness) For each race the regression models describing the variation in skinfold thickness were similar to those of BMI.
  • For both races, total energy, total grams of fat intake & the physical activity diary scores were not found to be independently related to skinfold thickness.

Total Energy:

Total energy intake was not independently & significantly associated with BMI & skinfold thickness in either black or white girls.

Interaction terms:

  • Significant interaction term between race & dietary fat in the regression analysis for skinfold led to different regression models for black & white girls.
  • It is possible that racial differences in eating patterns result in different sources of fat being prominent in the diet or better identified & quantified by the food record.
Author Conclusion:
Taken together overall, these results suggest that television viewing, dietary fat, & physical activity are important determinants of body weight and adiposity in children,
Funding Source:
Government: NHLBI
University/Hospital: University of California, Berkeley, Children’s Hospital Medical Center, Group Health Association, Maryland Medical Research Institute,
Reviewer Comments:

Strengths

  • Large sample size,
  • Study sample included both black & white girls.

Limitations

  • The median levels of physical activity measured in two ways were not fully consistent with each other.
  • High intra-individual variation encountered in dietary estimate.
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? N/A
  3. Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? N/A
  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? N/A
  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? N/A
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? N/A
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) N/A
  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? N/A
  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? N/A
  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? 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? 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? N/A
  8.3. Were statistics reported with levels of significance and/or confidence intervals? N/A
  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)? N/A
  8.6. Was clinical significance as well as statistical significance reported? N/A
  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