PWM: Family Influences (2006)

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

To examine the strength of the relationship between parental control over intake and children’s degree of overweight in a large population-based sample of third-grade children with diverse ethnic and socioeconomic backgrounds.

Inclusion Criteria:

Third grade students and their parents or guardians from 13 northern California public elementary schools.

Exclusion Criteria:

Children with no parent interview information.

Description of Study Protocol:

Trained personnel collected anthropometric measures from the children and parents or guardians were interviewed over the telephone.

Statistical Analysis

  • T-tests and Chi square:
    • To examine for possible bias due to nonparticipation or missing data
    • To test for differences between boys and girls 
  • Spearman correlation coefficients:
    • To determine association between parental control over children's eating and body fatness (BMI and triceps skinfold; for boys and girls separately
    • To test the association between parental control over children's food intake and household educational level
    • Parents' perceptions of their own weight, parents' perceptions of their child's weight and child's age 
  • Multiple linear regression:
    • To investigate the independent relationship of parental control over children's eating and BMI, entering control variables as covariates.
Data Collection Summary:

Dependent Variables

  • Children’s BMI (kg per m2)
  • Tricep skinfold thickness (measured)

Independent Variables

  • Parental Control over their Children’s Food Intake (six-item questionnaire developed by Birch)
  • Parental control was assessed using the following questions:
    • When my child does not finish dinner, he/she should not get dessert
    • My child should always eat all of the food on his/her plate
    • Generally, my child should only be permitted to eat at set mealtimes
    • My child often has to be strongly encouraged to eat things he/she doesn’t like because those foods are often good for him/her
    • My child should be strongly reprimanded for playing or fiddling with food
    • I have to be especially careful to make sure my child eats enough.

Control Variables

  • Gender
  • Household education level
  • Parents’ perception of their own weight: 'Underweight'; 'about the right weight'; 'overweight'
  • Parents’ perception of their children’s weight: 1 (underweight) to 5 (overweight) scale 
  • Children’s age
  • Children’s ethnicity: Parent interview).
Description of Actual Data Sample:
  • N:
    • Eligible: 985
    • Participated: 957
    • Complete data for analysis: 792 (Male=397; Female=395)
  • Age: Male: 8.5±0.4; Female: 8.4±0.4, P<0.05
  • Ethnicity: Diverse ethnic
  • SES: Diverse socioeconomic backgrounds
  • Location: Northern California.
Summary of Results:

Association Between Parental Control and Children's Intake

  • Girls: The relationship between parental control over children’s intake was inversely and significantly correlated with BMI (r=-0.12, P<0.05) and triceps skinfold thickness (r=-0.11, P<0.05). That is, greater measures of parental control was associated with lower BMI and skinfold thickness.
  • Boys: The relationship between parental control over children’s intake and both measures of overweight were close to zero and not statistically significant
  • The strength of the relationships between parental control over children's intake and BMI were not statistically significantly different between girls and boys when directly comparing the two correlation coefficients after Fisher's Z-transformations
  • Exploratory analysis of association betweeen parental control over intake and children's BMI by gender for Whites, Asians, and Latino/Hispanic:
    • Correlations for girls: Asian: r=-0.15; White: r=-0.11; Latino/Hispanic: r=-0.03
    • Correlations for boys: Asian: r=-0.08; White: r=-0.09; Latino/Hispanic: r=0.02.

Correlations Among Variables by Gender


Highest Household Educational Level

Parents' Perception of their Weight Parental Control over Intake Children's Age Children's BMI

Highest household educational level






Parents' perception of their own weight


Parental control over children's intake


-0.13** ---    
Children's age




Children's BMI






Children's triceps skinfold






Highest household educational level ---        
Parents' perception of their own weight 0.03 ---      
Parental control over children's intake -0.02 -0.15** ---    
Children's age -0.07 0.02 0.00 ---  
Children's BMI -0.0 0.21** -0.02



Children's triceps skinfolds






* P< 0.05;  ** P<0.01;  *** P<0.001

Multivariate Analysis

  • After controlling for covariates, parental control over intake was marginally significantly related to girls' BMI (P=0.05)
  • Two covariates remained significant: Parents' perception of their own weight (P<0.001) and household educational level (P<0.001).

Exploratory Analysis (Parental Control Over their Children's Intake and Their Perceptions of their Children's Weight)

  • Parents who controlled their daughters’ intake were more likely to perceived their daughters as underweight
  • Of the six questions, five (items two through six) could be combined into a single factor that explained 35% of the variance in an exploratory analysis. While this factor was modestly associated with girls' BMI, the association disappeared when a multivariate analysis was performed (P=0.07).


Author Conclusion:
  • Previous observations of the influence of parental control over intake among three- to five-year old pre-schoolers in middle-class white families did not generalize to eight- to nine-year olds in families of diverse socioeconomic and ethnic backgrounds. The relationship between parental behaviors and children’s weight status is complex. 
  • Parents of three- to five-year olds may have more influence over their children’s eating behaviors than parents of eight- to nine-year olds. As girls reach pre-adolescence the impact of parental control over food intake may be diluted by influences from their peers, mass media and the school environment.
Funding Source:
Government: NIH, NHLBI, AMA, PHS
Foundation associated with industry:
Reviewer Comments:


  • Large multi-ethnic population-based sample
  • Not in a laboratory setting.


  • The scale items (six-item questionnaire developed by Birch) were measuring different types of parental control, such as encouragement or restriction over their children’s intake. The exploratory analysis revealed that parents who controlled their daughter’s intake were more likely to view them as underweight.
  • The scale was developed to assess parental control over intake of younger (three to five year old) children.  Therefore, potential relationships may be obscured in this sample.
  • Five of the six questions could be interpreted as pressure to eat (as one form of control)
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? ???
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? Yes
  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.) 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? 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? ???
  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.) ???
  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? N/A
  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? N/A
  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