PDM: Prediabetes (2013)

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

To evaluate the effectiveness of lifestyle interventions in people with impaired glucose tolerance (IGT).

Inclusion Criteria:
  • Men and women
  • European origin
  • Ages 24-75 years
  • Diagnosis of IGT identified on two consecutive OGTTs (the second within two to 12 weeks of the first).
Exclusion Criteria:
  • Pregnant
  • Following a therapeutic diet
  • Unable to undertake physical activity.
Description of Study Protocol:


  • From the Royal Victoria Infirmary between the years 1994 to 1998
  • Allocation was done on the baseline appointment. 


  • Randomly assigned one intervention and one control group at the Royal Victoria Infirmary between the years 1994 to 1998
  • Allocation was done on the baseline appointment
  • Participants in the control group were offered no dietary or physical activity advice for the duration of the study. 

Blinding Used 

Researchers performed randomization to group allocation. 


  • Regular motivational counseling from a National Health Service dietitian and physiotherapist based on the "stages of change" model of behavioral change
  • Intervention participants had 12 review appointments over 24 months follow-up
  • Review appointments were on an individual basis, each lasting 15 to 20 minutes, with the dietitian and physiotherapist
  • In the first six months, there were three such appointments at two weekly intervals
  • There was one after nine months and five at two monthly intervals between 12 and 24 months. 

Statistical Analysis

  • Independent sample T-test
  • Logistic regression
  • Analysis of covariance. 
Data Collection Summary:
  • Timing of measurements: Baseline, six, 12 and 24 months
  • Dependent variables
    • Diet recorded on four-day food diaries consisting of two weekdays and two weekend days. Quantified by a food atlas.
    • Physical activity was self reported using a lifestyle questionnaire
    • Body weight was measured lightly clothed on SECA scales
    • Fasting plasma glucose was serum sample
    • Two-hour plasma glucose
    • Insulin sensitivity was assessed by the short ITT
    • Serum lipids ugins DAX analyser
  • Independent variables: Motivational counseling 
  • Control variables: No motivational counseling.
Description of Actual Data Sample:
  • Initial N: Control 22 males, 10 females; Intervention 17 males, 20 females
  • Attrition (final N): Control 24 (75%); Intervention 30 (81%)
  • Age: Control 57.5 years; Intervention 58.2 years
  • Ethnicity: European
  • Other relevant demographics: None
  • Anthropometrics:
    • Mean resting pulse lower in the control group who reported in a larger proportion of engaged physical activity than the intervention group
    • Also higher proportionof women than men in the intervention group
  • Location: Newcastle upon Tyne, UK.


Summary of Results:



Treatment Group

Measures and Confidence intervals

Control group

Measures and Confidence intervals

Statistical Significance of Group Difference

Diet (Change in Total Fat)

-16.7g fat at 12 months

-24.4g fat at 24 months

-0.43g fat at 12 months

-6.5g fat at 24 months



Physical Activity

 34.3 % at 12 months

32.1 % at 24 months

 7.1 % at 12 months

-4.2 % at 24 months



Body Weight

 -1.1kg at 12 months

 -1.8kg at 24 months

 1.5kg at 12 months

 1.5kg at 24 months



Insulin Sensitivity

-1.6mU/L at 12 months

0.10mU/L at 24 months

-0.1mU/L at 12 months

-0.80mU/L at 24 months



 Other Findings

  • Decreases in fasting serum insulin was significant at six and 12 months, but the effect was not detectable at 24 months
  • Despite the improvements in insulin sensitivity, there were no improvements in glucose tolerance during follow-up
  • Fasting serum NEFA,(Non-esterified Fatty Acids), decreased in the intervention group after six months and persisted through 24 months
  • There were more dropouts in the control group than in the intervention group, suggesting that the intervention was acceptable to the participants. 
Author Conclusion:
  • The authors concluded that the purpose of this study was to assess the impact of counseling on risk factors for CHD and Type 2 diabetes
  • Most lifestyle studies have more intense interventions such as 24 review appointments vs. the six appointments offered in this study
  • Even though there were no changes in the CHD risk factors in this study, there did result statistically significant changes in several cardiovascular risk factors such as total body weight and whole body sensitivity.
Funding Source:
Reviewer Comments:
  • The authors did a thorough analysis on their findings, discussed the limitations and interpreted the results in an organized format
  • The authors also explained the differences in standard lifestyle findings vs. this study's goal, which was not designed to assess the impact of counseling on health outcomes, but rather on the risk factors for CHD and Type 2 diabetes
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.) 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? 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? 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? Yes
  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? ???
  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? 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)? 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? 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? ???
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? ???