PDM: Prediabetes (2013)


Perala MM, Hatonen KA, Virtamo J, Eriksson JG, Sinkko HK, Sundvall J, Valsta LM. Impact of overweight and glucose tolerance on postprandial responses to high- and low-glycaemic index meals. Br J Nutr. 2011; 105(11): 1,627-1,634.

PubMed ID: 21262063
Study Design:
Randomized Crossover Trial
A - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:

To examine the effects of overweight and glucose tolerance on the glucose, insulin and lipid responses to a high-GI and a low-GI meal. The secondary aim was to study the effect of body mass index (BMI) and glucose tolerance on the relative glycemic response (RGR) of the meals.

Inclusion Criteria:

Body mass index (BMI) less than 24.9kg/m2, aged 62 to 72 years old.

Exclusion Criteria:
  • Smoking
  • Milk allergy
  • Regular medication that would impact glucose or lipid metabolism
  • Gastrointestinal disease influencing absorption
  • First-degree family history of type 2 diabetes.
Description of Study Protocol:


Randomized crossover trial.

Blinding Used 

Implied with measurements.


Participants consumed two different test meals, a high-GI meal (calculated GI 81) or a low-GI meal (calculated GI 33) and a control meal twice and a glucose solution in randomized order at one-week intervals.

Statistical Analysis

The independent sample T-test with Bonferroni's corrections was used for testing the differences between study groups. Insulin responses were non-normally distributed; statistical significance was therefore assessed by using the non-parametric Wilcoxon test. All statistical analyses were done using SPSS for Windows version 15.0. The level of significance was P<0.05. Results are expressed as means with their standard errors or standard deviations.

Data Collection Summary:

Timing of Measurements

Body weight was measured in the clinic. Blood was drawn (finger-prick capillary blood sample and intravenous blood sample). Participants then consumed test meal (either a high-glycemic meal, GI 81 or low-glycemic index meal, GI 33) and a glucose solution in one-week intervals. 

Dependent Variables

  • Body weight: Measured in the clinic; changes of 2kg in weight were allowed during the study
  • Blood glucose: Blood drawn in the clinic via:
    • A finger-prick capillary blood sample (0.5ml per sample) before the meal and at minutes 15, 30, 45, 60, 90 and 120
    • An intravenous blood sample (8ml per sample) before the meal and at minutes 30, 60, 120, 180, 240 and 300.

Independent Variables

  • All participants consumed two different test meals, a high-glycemic index meal (GI 81) and a low-glycemic index meal (GI 33) plus a glucose solution, in randomized order at one-week intervals.
Description of Actual Data Sample:

Initial N


Attrition (final N):

48 subjects:

  • 12 normal weight NGT (six males, six females)
  • 12 overweight NGT (six males, six females)
  • 12 normal weight IGT (five males, seven females)
  • 12 overweight IGT (four males, eight females).


62 to 72 years old.

Other Relevant Demographics

24 were normal weight (BMI 20 to 24.9kg/m2) and 24 were overweight (BMI 27.5 to 34.9kg/m2). Both groups included 12 participants with normal glucose tolerance and 12 with impaired glucose tolerance.


Fasting serum glucose and triglycerides did not differ between groups, whereas fasting insulin levels (P<0.001) and insulin resistance (P<0.001) were significantly higher among overweight participants with impaired glucose tolerance than among normal-weight subjects with normal glucose tolerance.




Summary of Results:

Key Findings

Test Meal Normal Weight, Normal Glucose Tolerance Overweight, Normal Glucose Tolerance P Normal Weight, Impaired Glucose Tolerance P Overweight, Impaired Glucose Tolerance P
Low-GI meal       
Glucose, two hours (mmol per minute per L) 80±14 100±10 0.24 139±13 0.005 132±16 0.024
Insulin, two hours (ρmol per minute per L) 12,307±1,830 26,340±10,248 0.21 15,718±1,638 0.16 29,797±4,750 0.002
High-GI meal       
Glucose, two hours (mmol per minute per L) 183±22 252 ±50 0.22 303±23 0.001 248±22 0.049
Insulin, two hours (ρmol per minute per L) 19,737±2,690 33,678±9,477 0.18 21,966±1,951 0.51 41,416±5,316 0.004
Glucose solution       
Glucose, two hours (mmol per minute per L) 227±18 340±42 0.0222 401± 33 <0.001 321  
  • The glucose responses of subjects with IGT differed significantly from those of subjects with NGT
  • The highest insulin responses to both meals were observed in overweight subjects with IGT
  • Physiological characteristics did not influence TAG or NEFA responses or the RGR of the meals
  • The LGI meal resulted in lower glucose (P<0.001) and insulin (P<0.001) responses, but higher TAG responses (P<0.001), compared with the HGI meal
  • The GI of the meals did not affect the NEFA responses.


Author Conclusion:

The authors concluded that postprandial glucose responses are affected only by glucose tolerance, whereas overweight and impaired glucose tolerance occurring simultaneously have an impact on insulin responses. Overweight and glucose tolerance do not have an effect on postprandial lipid responses.

Funding Source:
Government: The National Institute for Health and Welfare, Finland
University/Hospital: Helsinki University Central Hospital, Vaasa Central Hospital
Reviewer Comments:

Recruitment methods not described.  Small numbers of subjects in groups.

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.) N/A
  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%.) N/A
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? N/A
  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? 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.) 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? No
  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)? 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? 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