NC: Motivational Interviewing (2008)

Study Design:
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Quality Rating:
Research Purpose:

The purpose of this study was to develop, implement, and evaluate the efficacy of an intensive intervention program (IIP) based on motivational interviewing to motivate participants within the dietary study of the Women's Health Initiative (WHI) to meet the study's nutritional goals.

Inclusion Criteria:
  • Assignment to the Women's Health Initiative Dietary Modification Intervention (WHIDMI)
  • Assigned to at least six months of the intervention protocol by the first Women's Health Initiative (WHI) annual visit
  • Completion of a Food Frequency Questionnaire at the first annual WHI follow up visit
  • A target date for the first annual WHI visit between October 1996 and May 1997
  • Expression of willingness to continue the dietary modification (DM) intervention.
Exclusion Criteria:

Participating Clinical Center staff reviewed the eligible participants and removed any that were experiencing severe personal or family illness, making them unable to respond to telephone contact or make visits to the clinical center.

Description of Study Protocol:


  • Potential participants were selected from the main WHI database based on eligibility requirements
  • The study was conducted at three WHI clinical centers chosen because they were doing well in the WHI.


WHI dietary intervention participants from three clinical centers were randomly assigned to either intervention or control status.

Blinding Used

All staff reviewing Food Frequency Questionnaire data were unaware of participants' WHIDMI randomization status.


  • Participants randomly assigned to IIP intervention received three individual motivational interviewing contacts from a dietitian, plus the usual WHI Dietary Intervention.
  • Participants randomly assigned to IIP control received the usual WHI dietary modification intervention.

Statistical Analysis

  • Changes in dietary fat intake by IIP study were examined using paired T-test to determine the main outcome of the study
  • The effects of the IIP intervention by IIP baseline fat intake to determine possible individual differences in IIP effects were analyzed using T-tests
  • Participation variables were also examined using T-tests.
Data Collection Summary:

Timing of Measurements

The follow-up period for this study was one year.

Dependent Variables

  • Variable One: Baseline percent energy from fat measured using a Food Frequency Questionnaire 
  • Variable Two: Effect of IIP Intervention on percent energy from fat measured using a Food Frequency Questionnaire.

Independent Variables

Participants assigned to the IIP intervention received the motivational intervention, in addition to their normal WHIDMI protocol.

Control Variables

Participants in the IIP control group received only their normal WHIDMI activities.

Description of Actual Data Sample:
  • Initial N: 175 women
  • Attrition (final N): 164 (N=11 or 6.3% did not provide FFQs at their IIP follow-up visit).


  • Intervention (N=82): 65.1±6.8
  • Control (N=82): 65.5±5.9.


  • Intervention
    • White: 73 (89%)
    • African-American: Eight (10%)
    • Other: One (1%).
  • Control
    • White: 75 (92%)
    • African-American: Six (7%)
    • Other: One (1%)

Other Relevant Demographics

Education Intervention Control
High school/GED or below 35 (43%) 29 (24%)
School after high school 23 (28%) 34 (42%)
College degree or higher 24 (29%) 24 (29%)
Marital Status at screening    
Married or living as married 57 (70%) 55 (67%)
Not married 25 (30%) 27 (33%)


BMI at screening

  • Intervention: 30.1±6.1
  • Control: 29.0±5.1.


Three WHI clinical centers.

Summary of Results:

 Effect of IIP Intervention on FFQ Percentage of Energy from Fat


Intervention (N=82)

Measures and confidence intervals

Control group (N=82)

Measures and confidence intervals

Statistical Significance of Group Difference

IIP Baseline





Statistically significant difference between groups


IIP Follow-up








Author Conclusion:

The results of this study indicate that a protocol based on motivational interviewing and delivered through contacts with trained dietitians is an efficacious way to further lower dietary fat intake among participants exposed to ongoing intervention.

Funding Source:
Government: NIH
Reviewer Comments:

The dietary interventions in the WHI are intensive. The first year included 18 group sessions that provided dietary and behavioral skills information. During the second year, the intervention was facilitated through group sessions held once every three months. The additional intervention of this study consisted of three individual motivational interviewing contacts with a dietitian in addition to the regularly scheduled WHIDMI group sessions.

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? 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")? Yes
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? Yes
  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? Yes
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? Yes
  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? Yes
  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? N/A
  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)? N/A
  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