PDM: Prediabetes (2013)


Oldroyd JC, Unwin NC, White M, Imrie K, Mathers JC, Alberti KGMM. Randomized controlled trial evaluating the effectiveness of behavioral interventions to modify cardiovascular risk factors in men and women with impaired glucose tolerance: Outcomes at six months. Diabetes Res Clin Pract. 2001; 52 (1): 29-43.

PubMed ID: 11182214
Study Design:
Randomized Controlled Trial
A - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:

To test whether counseling from a dietitian and a physiotherapist would result in improvements in diet or aerobic physical activity, improvements in glucose tolerance and insulin sensitivity and improvement in cardiovascular risk factors after six months.

Inclusion Criteria:
  • Aged 24 to 75 years
  • Impaired glucose tolerance identified on two consecutive oral glucose tolerance tests (OGTT).
Exclusion Criteria:
  • Aged under 24 years or over 75 years
  • Normal glucose tolerance
  • Pregnant women
  • Following a therapeutic diet
  • Individuals with a medical condition preventing them from undertaking moderate physical activity.
Description of Study Protocol:


Individuals with impaired glucose tolerance (IGT) were recruited to the study from the following three sources:

  1. Research studies conducted in the Department of Medicine at the University of Newcastle between 1993 and 1994
  2. Local hospital biochemistry laboratory databases
  3. General Practitioner (GP) surgeries. 


Randomized controlled trial with one intervention and one control arm.

Blinding Used

  • Participants were randomly allocated using a random number table to the Intervention or the Control Group at the first baseline appointment
  • Researchers performing the randomization were blinded to the group allocation.


  • The intervention consisted of regular counseling from a dietitian and a physiotherapist using the stages of change model 
  • The Intervention Group received a dietary assessment during a one-on-one interview with a dietitian, using the baseline food diary
  • The dietitian used stage-specific motivational interviewing to develop individual goals for behavior change 
  • Participants were encouraged to eat more fruits and vegetables, reduce fat intake, reduce sugar intake and achieve a BMI below 25kg/m2 
  • The physiotherapist assessed the participants' level of physical activity at baseline and provided a graded physical activity plan designed to achieve 20 to 30 minutes of aerobic activity two to three times per week.

Statistical Analysis

  • All analysis was performed on an intention-to-treat basis 
  • An independent sample T-test was used to compare differences in change between the Control and Intervention Groups.
Data Collection Summary:

Timing of Measurements

All intervention and control participants had three separate appointments at baseline and at six months.

Dependent Variables

  • OGTT was performed and fasting one- and two-hour venous blood samples were taken to measure plasma glucose and serum insulin and C-peptide concentrations
  • Lipid concentrations were measured on fasting blood samples, including estimates on cholesterol, triglycerides, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol and non-esterified fatty acids
  • Glycosylated hemoglobin was measured
  • Fibrinogen concentrations were measured
  • Weight was measured and BMI was calculated
  • Waist and hip circumference was measured and waist-to-hip ratio was calculated
  • Blood pressure was measured
  • A self-completed questionnaire on health-related behaviors, including physical activity, was completed
  • Insulin-sensitivity was assessed using the short insulin tolerance test
  • The shuttle test was used to assess physical activity and resting pulse was recorded. 

Independent Variables

  • Randomized group allocation (intervention vs. control)
  • A four-day food diary was completed comprising two weekdays and two weekend days. Amounts consumed were quantified using a food atlas during an interview with a dietitian.
Description of Actual Data Sample:
  • Initial N: 78 participants randomized into Intervention vs. Control Groups (percentage male was not reported)
  • Attrition (final N): 67 participants (38 men and 29 women) completed the study. Of these 67 participants, 32 were in the Control Group and 35 were in the Intervention Group.
  • Age: 24 to 75 years
  • Ethnicity: European origin
  • Other relevant demographics: None reported 
  • Anthropometrics: At baseline, there was no significant difference between intervention and control participants with respect to age or outcome measures. There were fewer women in the Control Group, compared to the Intervention Group.
  • Location: Royal Victoria Infirmary, Newcastle upon Tyne, UK.
Summary of Results:

Nutrient Intake

  • Significant differences were observed in changes from baseline to six months between the Intervention and Control Groups in:
    • Total fat intake (-21.8g per day; 95% CI, -37.8 to -5.8; P=0.008)
    • Monounsaturated fat intake (-6.8g per day; 95% CI, -12.6 to -1.01; P=0.022)
    • Polyunsaturated fat intake (-5.0g per day; 95% CI, -9.8 to -0.19; P=0.042).
  • Changes in energy intake, saturated fat intake, polyunsaturated fat intake, sucrose, fiber and starch did not reach significance.

Resting Pulse, Shuttle Walking Test and Reported Physical Activity

  • Significant differences were observed in changes from baseline to six months between the Intervention and Control Groups in:
    • Resting pulse (-3.6 beats per minute; 95% CI, -7.1 to -0.22; P=0.038)
    • Vigorous activity reported (number of participants undertaking vigorous activity at least three times per week, 30.1%; 95% CI, 4.3 to 52.7; P=0.021).
  • Distance walked and recovery pulse were not significantly different.

Anthropometry and Mean Blood Pressure

  • Significant differences were observed in changes from baseline to six months between the Intervention and Control Groups in:
    • Weight (-2.0kg; 95% CI, -3.2 to -0.8; P=0.001)
    • BMI (-0.95kg/m2; 95% CI, -1.5 to -0.4; P=0.001)
    • Systolic blood pressure (-7.6mmHg; 95% CI, -15.2 to -0.006; P=0.050)
    • Diastolic blood pressure (-4.9mmHg; 95% CI, -9.7 to 0.04; P=0.052).
  • Changes in waist circumference, hip circumference and waist-to-hip ratio between groups did not reach significance.

Glucose Tolerance, Plasma Insulin and C-Peptide Concentrations

  • Significant differences were observed in changes from baseline to six months between the Intervention and Control Groups in:
    • Fasting insulin (-3.4mU per L; 95% CI, -5.8 to 1.1; P=0.005)
    • Homeostasis model assessment (insulin resistance) (-0.99; 95% CI, -1.7 to -0.25; P=0.01)
    • Two-hour insulin (-34.1mU per L; 95% CI, -66.2 to -2.1; P=0.037)
    • Fasting C-peptide (-0.14nmol per L; 95% CI, -0.3 to 0.002; P=0.053)
    • Two-hour C-peptide (-0.07nmol per L; 95% CI, -1.4 to -0.02; P=0.044).
  • Changes in fasting plasma glucose, two-hour fasting plasma glucose, glycosylated hemoglobin and estimate of insulin-sensitivity (slope of the curve) between groups did not reach significance.

Blood Lipid Concentrations

  • Significant differences were observed in changes from baseline to six months between the Intervention and Control Groups in: Fasting non-esterified fatty acids (-0.19mmol per L; 95% CI, -0.29 to -0.08; P=0.001)
  • Changes in total cholesterol, HDL-cholesterol, LDL-cholesterol, triglycerides, apolipoprotein A-1, apolipoprotein B and fibrinogen between groups did not reach significance
  • Changes in blood pressure were of borderline significance (P=0.050 for systolic blood pressure and P=0.052 for diastolic blood pressure)
  • There were no significant differences between groups in terms of change in mean two-hour plasma glucose, triglycerides, HDL-cholesterol, serum cholesterol, waist circumference or waist-to-hip ratio. Renal outcomes were not reported.
Author Conclusion:
  • Dietary and physical activity counseling in individuals with impaired glucose tolerance has an effect on nutrient intake, physical activity uptake, cardiovascular risk factors and insulin sensitivity after six months. No effect on glucose tolerance was observed with counseling after six months.
  • The results of the study indicate that interventions, which use the stages of change model and are potentially applicable in primary care, can result in reduced risk factors for CHD and Type 2 DM in individuals with IGT after six months. 
Funding Source:
Government: Northern & Yorkshire NHS Research and Development
British Heart Foundation
Other non-profit:
Other: Royal College of General Practitioners
Reviewer Comments:
  • Strong study protocol
  • Results could have been enhanced with multivariate analysis, which was not performed
  • Secondary factors which may have effected outcomes, such as changes in health, were not reported, but assumed to be measured by a self-completed health questionnaire
  • Power calculation was performed, but recruitment fell below the threshold number calculated, therefore it is difficult to determine whether non-significant results may have reached significance with adequate numbers.
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")? 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? 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? 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? 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? ???
  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)? No
  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? Yes
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