Health Disparities

HD: Effectiveness of Nutrition Intervention Methods (2010)


Gurka MJ, Wolf AM, Conaway MR, Crowther JQ, Nadler JL, Bovbjerg VE. Lifestyle intervention in obese patients with type 2 diabetes: impact of the patient's educational background. Obesity (Silver Spring). 2006;14(6): 1085-1092.

Study Design:
Randomized Controlled Trial
A - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:

The purpose of this study was to determine whether obese patients with type 2 diabetes of different educational backgrounds respond differently to a lifestyle intervention program.

Inclusion Criteria:
  • Physician-confirmed type 2 diabetes
  • Use of diabetes medications
  • Body mass index (BMI) 27 or more
  • Age 20 years or older
  • Ability to comprehend English
  • Membership in the Southern Health Services health plan.
Exclusion Criteria:
  • Pregnancy
  • Cognitive limitations
  • Medical reasons precluding dietary and physical activity modifications.
Description of Study Protocol:


Invitations were mailed to eligible participants identified from Southern Health Services data. Then participants initiated contact with study personnel.


Eligible participants were randomly assigned to either the intervention group or control group.

Blinding used

Study personnel were blinded to the random allocation schedule until assignment.


  •  Intervention group:
    • One registered dietitian (RD) case manager met with patients individually and by phone for assessment, goal setting, education and support
    • Goals were individualized but based on national dietary recommendations for obese people with type 2 diabetes
    • The RD measured weight and waist circumference, followed laboratory results and discussed patient-care issues with physicians when appropriate
    • Six individual sessions (total of four hours) and six one-hour small-group sessions were held throughout the year
    • Brief phone contacts were provided monthly for support.
  • Control group: Received usual care (educational material and were invited to join other weight-management or diabetes care programs).

Statistical Analysis

  • Repeated-measurement models used to compare two groups relative to changes in weight and waist circumference
  • Change-from-baseline values were modeled at four, six, eight and 12 months, comparing mean trajectories among education levels and between two groups
  • Intent-to-treat methods were used in comparing the two groups; the models used all of the available data on participants, including those who dropped out of the study or had intermittently missing data
  • Various baseline covariates were considered in the fitted models, including age, race, sex and smoking status.
Data Collection Summary:

Timing of Measurements

Baseline and four, six, eight and 12 months

Dependent Variables

  • Weight (kg)
  • Waist circumference (cm)

Independent Variables

  • Treatment group (intervention vs. control)
  • Education level (without a college degree vs. college degree or higher)

Control Variables

  • Race/ethnicity (white vs. non-white)
  • Age
  • Sex
  • Smoking status.
Description of Actual Data Sample:

Initial N

  • 147 participants randomly assigned to one of the two groups
  • Baseline characteristics obtained on 144 (72 per group).

Attrition (final N)

118 individuals (80%) completed the intervention.

Mean Age (years±standard deviation)

  • No college degree, control group: 53.8±7.8
  • No college degree, treatment group: 53.5±7.6
  • College degree, control group: 52.4±9.7
  • College degree, treatment group: 53.2±8.6

Ethnicity, Number (Percent) of White Participants

  • No college degree, control group: n=32 (68%)
  • No college degree, treatment group: n=33 (79%)
  • College degree, control group: n=21 (84%)
  • College degree, treatment group: n=28 (93%) 

Sex, Number (Percent) of Women

  • No college degree, control group: n=31 (66%)
  • No college degree, treatment group: n=28 (67%)
  • College degree, control group: n=11 (44%)
  • College degree, treatment group: n=17 (57%)

Anthropometrics (e.g., were groups same or different on important measures)

  • Mean weight (kg)±standard deviation:
    • No college degree, control group: 105.1±22.0
    • No college degree, treatment group: 105.4±25.3
    • College degree, control group: 110.4±31.4
    • College degree, treatment group: 107.9±23.1
  • Mean waist circumference (cm)±standard deviation:
    • No college degree, control group: 115.9±15.2
    • No college degree, treatment group: 117.4±16.5
    • College degree, control group: 118.6±15.8
    • College degree, treatment group: 119.1±16.6
  • None of the baseline characteristics were significantly associated with intervention assignment
  • Only income and race were significantly associated with education level.



Summary of Results:

Key Findings

  • 100% of intervention group who completed the study attended all of the individual sessions
  • 75% of intervention group who completed study attended four or more group classes
  • Number of classes attended was not associated with education or outcomes. 
  • Weight outcome: In the model adjusting for baseline weight and other potential confounders (age, sex, race and smoking), the education-by-intervention group interaction was significant (P=0.02). The education-intervention interaction with time was not significant (P=0.51).
    • By 12 months in the control group, individuals in the lower education group gained a model-predicted 1.71kg more than similar individuals with college degrees (95% confidence interval: -1.29, 4.71)
    • By 12 months in the treatment group, individuals in the lower education group lost a model-predicted 3.30kg more than similar individuals with college degrees (95% confidence interval: -6.54, -0.07).
  • Waist circumference outcome: In the model adjusting for baseline waist circumference and other potential confounders, the education-by-intervention group interaction was significant (P=0.01), but the difference across time was not significant (P=0.12).  
    • By 12 months in the control group, individuals in the lower education group gained a model-predicted 3.67cm in waist circumference more than similar individuals with college degrees (95% confidence interval: -0.04, 7.38) 
    • By 12 months in the treatment group, individuals in the lower education group lost a model-predicted 4.95cm more in waist circumference than similar individuals with college degrees (95% confidence interval: -8.85, -1.04). 
Author Conclusion:

This analysis of a lifestyle intervention trial suggests that those with less education may actually respond better to this education-oriented intervention, a notion that is initially counterintuitive. However, those who are less educated are less knowledgeable about obesity in general may be more receptive to the information gained from an education-based intervention. Those with higher education, who may already have relatively greater knowledge about obesity control, may not benefit equally from this type of intervention. Similar results in broader studies will serve as motivation to tailor interventions based on participant characteristics, such as education level.

Funding Source:
Government: National Institute of Diabetes and Digestive and Kidney Diseases
University/Hospital: University of Virginia General Clinical Research Centetr
Other: American Dietetic Association
Reviewer Comments:

This seems to be a well-designed and -described study. Although the authors did not describe how weight and waist circumference were derived, they did state that measurements were taken by trained personnel.  One potential confounder that was not examined was the use of diabetic medications that may affect weight. Although the number of prescription and diabetes medications at baseline were described, the actual type of medication was not described, nor were any changes in the medication regimen over time. 

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) 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")? 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? ???
  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? No
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? No
  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.) No
  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? ???
  6.6. Were extra or unplanned treatments described? ???
  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? ???
  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? ???
  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? No
  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