PWM: Family Influences (2006)


Davison KK, Birch LL. Obesigenic families: Parents’ physical activity and dietary intake patterns predict girls’ risk of overweight. Int'l J Obes. 2002; 26: 1,186-1,193.

PubMed ID: 12187395
Study Design:
Panel design.
C - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:

To determine whether distinct obesigenic and non-obesigenic family clusters could be identified based on mothers’ and fathers' dietary and activity patterns and to assess whether cluster membership could be used to predict differences in their daughters’ body composition.

Inclusion Criteria:
  • Non-Hispanic white girls five years of age at the study's onset and their parents
  • Living in Pennsylvania
  • Children were living with both biological parents.
Exclusion Criteria:
  • Girls with severe food allergies
  • Girls with chronic medical problems that affected food intake
  • Dietary restrictions involving animal products.
Description of Study Protocol:


  • Parents and daughters were recruited, using flyers and newspaper advertisements, for participation in a longitudinal study of the health and development of young girls from ages five to nine years
  • Families with age-eligible females living within a five-county radius received letters inviting them to participate in the study.

Study Duration

192 of the 197 families originally recruited were assessed again two years later when the girls were seven years old.


  • Parents visited the laboratory and completed questionnaires assessing diet and physical activity habits
  • Trained staff measured girls', mothers' and fathers' weight and height, and girls' tricep and subscapular skinfold thickness.

Statistical Analysis

Cluster Analysis: An exploratory multivariate procedure that assesses whether cases can be grouped together based on similarities.


Data Collection Summary:

Criterion Variables

  • Girls’ BMI at age five and seven
    • Calculated using the average of three measurements
    • Classified as overweight (BMI is 17.2 or more at age five and 18.0 or more  at age seven) or obese (BMI 19.3 or more at age five and 21.0 or more at age seven)
    • BMI values also converted to BMI percentiles using CDC 2000 growth charts
  • Girls' skinfold thickness at five and seven years of age (measured)
  • Parents’ BMI measured when their daughters were ages five and seven (classified as overweight and obese based on BMI cut-offs of 25 and 30, respectively.

Clustering Variables

  • Parents’ physical activity variable: Composite Activity Score of:
    • Sport participation (picked from a list of 22 activities)
    • Weekly exercise frequency [ranked from one to five ("never" to "always")]
    • Enjoyment of sport and activity (three-point response item) 
  • Parents’ dietary variable: Intake Composite Score of:
    • Total energy intake adjusted for body weight
    • Percentage of energy from fat (FFQ)
    • Dietary disinhibition (Dutch Eating Behavior Questionnaire)
  • Other measurements used in the analysis after the formation of the clusters
    • Change in girls’ BMI and skinfold thickness between ages five and seven years
    • Family income was assessed using Chi-Square between two clusters (obsegenic and non-obsegenic)
    • Parent education level and age was assessed using ANOVA between two clusters (obsegenic and non-obsegenic).
Description of Actual Data Sample:
  • Initial N: 197 families
  • Final N: 192 girls with both parents; it is unclear why five families were not measured at follow-up
  • Age: Five years of age at study start
  • Ethnicity: Non-Hispanic white families
  • SES: Families with mixed levels of SES and generally well-educated
  • Girls' BMI at age five ranged from 13.0 to 25.6; mean±STD=15.8±1.4
  • Mothers' BMI at age five ranged from 17.7 to 56.1; mean±STD=26.3±5.6
  • Fathers' BMI at age five ranged from 18.7 to 42.0; mean±STD=28.0±4.2
  • Location: Pennsylvania. 
Summary of Results:

The cluster analysis resulted in the formation of two distinct clusters: One cluster showed clear behavioral patterns that promote the development of overweight (obesigenic), while the other showed a clear absence of such patterns (non-obesigenic).

  • Families in obesigenic cluster were significantly less likely to report a family income of more than $50,000 (28%) compared to families in non-obesigenic cluster (43%, P<0.05)
  • There were no differences between clusters for parent education or age after controlling for income.

Income was then used as a covariate for the rest of the results, described below.

  • Families in the obesigenic cluster had mothers and fathers who reported below-average activity component scores and above-average intake scores, relative to the entire sample
  • Families in the non-obesigenic cluster had mothers and fathers who reported above-average activity component scores and below-average intake scores, relative to the entire sample
  • There was no difference between clusters for fathers' disinhibition scores
  • Among mothers, those in the obesigenic cluster reporting higher levels of disinhibition than mothers from the non-obesigenic cluster.

Then, the clusters were validated by assessing the predictive value of the clusters to identify differences in girls' and parents' body composition.

Consistent differences were noted between the two clusters in girls’ body composition and change in body composition.

  • Girls from families in the obesigenic cluster showed significantly greater increases in BMI between ages five and seven (after controlling for BMI at age five) and had significantly higher BMI scores at age seven. A similar pattern was noted for skinfold thickness.
  • Of the 14 girls who became overweight between ages five and seven, 11 (or 78%) were from families in the obesigenic cluster)
  • Controlling for Parental BMI: Differences in girls’ body composition were apparent even after controlling for parents’ BMI. The differences were attenuated, thereby indicating the importance of both genetic and environmental factors in predicting children’s weight status and change in weight status.
Author Conclusion:

Results from this study confirm the need to focus intervention efforts at the level of family, as it is unlikely that a child’s elevated weight status, poor eating habits and low levels of activity are isolated events in the family context. Rather, they are likely to reflect a general pattern of characteristics noted among parents and possibly siblings.

Characteristics of the family environment explain differences in children’s weight status over and above that explained by genetic susceptibility.

Funding Source:
Government: NIH
University/Hospital: Pennsylvania State University
Reviewer Comments:


  • Questionnaires had been validated and found to be reliable and valid
  • Intra-class correlation coefficients for skinfold measurements at age five and seven were all 0.90 or more 
  • Only one person collected skinfold measurements
  • Multiple measures of activity and intake were used to make a composite variable
  • Few families were lost at follow-up
  • Mothers and fathers were both assessed.


  • Convenience sample
  • Use of self-reported measures of activity and intake
  • External validity of the results is limited by the sample characteristics; results may differ for families from different ethnic and educational backgrounds or for sons.
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? 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) 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? 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? No
3. Were study groups comparable? N/A
  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? N/A
  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? No
  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%.) No
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? No
  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? 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.) Yes
  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? No
  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? 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? No
  7.7. Were the measurements conducted consistently across groups? N/A
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