PDM: Prediabetes (2013)

Study Design:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
  • To evaluate the impact of a 2-year combined diet and physical activity intervention program, according to general recommendations, on glucose tolerance in Dutch subjects at increased risk for developing (type 2) diabetes.
Inclusion Criteria:
  • >40 years old
  • Family history of diabetes or body mass index (BMI) =/> 25 kg/m2
  • Two oral glucose-tolerance test results of fasting glucose <7.8 mM and 2-hour glucose concentration between 7.8 and 12.5 mM
Exclusion Criteria:
  • Known or overt diabetes
  • Medication use known to interfere with glucose tolerance
  • Participation in regular vigorous exercise program
  • Participation in intensive weight reduction program during the last year before the study
Description of Study Protocol:


  • Subjects were selected from an existing cohort which was described in another paper


  • Eligible subjects were randomly assigned to the intervention group or control group by use of a randomization list and were stratified for sex and 2-hour plasma glucose concentration

Blinding used (if applicable)

  •  No

Intervention (if applicable)

  • Intervention group participated in regularly scheduled dietary and physical activity visits throughout the study.  Dietitians instructed individual subjects on recommendations for healthy eating based on the Dutch Nutrition Council guidelines.   Subjects were encouraged to increase their activity to 30 minutes of moderate physical activity at least 5 days per week.  Visits were scheduled at randomization, in 4-6 weeks after randomization, and then every 3 months.
  • Control group participants were given written information about diet and exercise but no individual programs were given.  Visits were only at randomization and yearly for annual measurements.

Statistical Analysis

  • Data is presented in mean ± SE
  • Differences between groups are tested with Student's t test for independent samples or by a X2
  • Changes between groups over time were assessed with an ANOVA for repeated measures
  • Corrrections were made for differences in sex and baseline values when analysis of covariance was used for comparisons among multiple groups
  • P value of <0.05 was considered statistically significant
Data Collection Summary:

Timing of Measurements

  •  Baseline (randomization), 1 year and 2 years.

Dependent Variables

  • 2-hour blood glucose concentration following oral glucose tolerance test (OGTT)
  • Fasting plasma glucose concentration
  • Insulin/insulin resistance [homeostasis model assessment (HOMA) index]
  • A1C
  • Body composition
  • Aerobic capacity

Independent Variables

  • Study group 

Control Variables

  •  Sex and baseline values
Description of Actual Data Sample:

Initial N: 114 (55 intervention group/59 control group)

Attrition (final N): 88 at 2 years (40 intervention group/48 control group)

Age: 55.6 ±  0.9 years intervention group/ 57.8 ± 1.0 years control group

Ethnicity: Dutch

Other relevant demographics: Positive family history in 25.5% intervention group and 35.5% control group

Anthropometrics: Both groups were similar in baseline measurements

Location: The Netherlands


Summary of Results:


Results: 1-year change

 Intervention Group

 Control Group

 p value

2-hour glucose (mM)*  -0.9 ± 0.3   +0.3 ± 0.3  <0.01
FPG (mM)

 -0.1  ± 0.1

 +0.1  ± 0.1



 -0.9 ± 0.3

 +0.1 ± 0.2


A1C (%)  -0.2 ± 0.1  -0.2 ± 0.1  ns

Body composition (% body fat)

 -1.7 ± 0.3  -0.7 ± 0.3  <0.05
Aerobic capacity (VO2 Max: L/min)  +0.11 ± 0.03  -0.01 ± 0.04  <0.05

  *1 mM of measured blood glucose is equivalent to 18 mg/dl measured blood glucose


Results: 2-year change

 Intervention Group

 Control Group

 p value

2-hour glucose (mM)*  -0.6 ± 0.3   +0.8 ± 0.4  <0.01
FPG (mM)

 +0.2  ± 0.1

 +0.5  ± 0.1



 -0.5 ± 0.5

 +0.7 ± 0.4


A1C (%)  +0.0 ± 0.1  -0.1 ± 0.1  ns

Body composition (% body fat)

 -1.0 ± 0.3  -0.5 ± 0.3  ns
Aerobic capacity (VO2 Max: L/min)  +0.09 ± 0.04  -0.03 ± 0.04  <0.05

  *1 mM of measured blood glucose is equivalent to 18 mg/dl measured blood glucose

Other Findings

  • Those subjects that were adherent to both diet and exercise interventions showed the largest reduction in the 2-hour blood glucose (-1.9 ± 0.6 mM) and largest reduction of weight (-6.2 ± 1.6 kg).  Adherence to diet intervention was defined as reaching 2 or 3 of the following goals:  total fat intake <35% energy, saturated fatty acid intake <10% energy; and fiber intake more than 3 grams/MJ.  Exercise adherence was defined as at least 1 hour/week in supervised exercise sessions during the 2 years of study intervention.
Author Conclusion:
Our results showed that a lifestyle intervention program according to general recommendations improves glucose tolerance, even in a less obese and more physically active population.
Funding Source:
Reviewer Comments:
2 hour fasting blood glucose improved ~ 22 mg/dl after the first year and ~ 25 mg/dl after the second year.
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? ???
  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? 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? 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.) 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? Yes
  6.6. Were extra or unplanned treatments described? No
  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)? ???
  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? No
  9.1. Is there a discussion of findings? No
  9.2. Are biases and study limitations identified and discussed? No
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