GDM: Carbohydrate (2001)


Vlachokosta FV, Piper CM, Gleason R, Kinzel L, Kahn CR.  Dietary carbohydrate, a Big Mac, and insulin requirements in type 1 diabetes.  Diabetes Care 1988;11(4):330-336.

PubMed ID: 3042309
Study Design:
Randomized Crossover Trial
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Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:
To determine the insulin requirements in 5 nonobese type 1 diabetic subjects who received isocaloric 40% and 60% mixed-carbohydrate diets for 4 days, each day consisting of 4 equal meals, followed by a Big Mac Attack lunch.
Inclusion Criteria:
  • Duration of diabetes ranged from 12 - 27 years
  • Ages at study ranged from 24 - 51 years
  • All patients had been treated before admission with subcutaneous injections of regular and NPH insulin twice daily
Exclusion Criteria:
  • No overt evidence of neuropathy, retinopathy, gastropathy, nephropathy or acute illness at the time of the study
Description of Study Protocol:


Methods not described.


Randomized Crossover Trial.

Blinding used (if applicable):  not possible 

Intervention (if applicable)

  • Subjects received isocaloric 40% and 60% mixed-carbohydrate diets for 4 days, each day consisting of 4 equal meals
  • On day 5, subjects received Big Mac Attack lunch consisting of Big Mac, french fries and milk shake

Statistical Analysis

Differences between insulin requirements for the 40% and 60% carbohydrate meals were tested for significance with paired Student's t tests.  Glucose levels and insulin requirements among the 4 meals were compared with one-way ANOVA followed by post hoc comparisons among means with least-squares means procedure.  Comparisons among the 40% and 60% carbohydrate meals and the Big Mac lunch were made with one-way ANOVA followed by post hoc comparisons among the means with a least-squares means procedure.

Data Collection Summary:

Timing of Measurements

Subjects received meals for 4 days, followed by 5th day of Big Mac Attack lunch.  Insulin requirements to maintain normoglycemia were calculated for each 24-hour period and for the 2 hours after each meal.

Dependent Variables

  • Insulin requirements directed by artificial beta-cell
  • Blood samples for measurements of FFA concentrations, free insulin and C-peptide

Independent Variables

  • Subjects received isocaloric 40% and 60% mixed-carbohydrate diets for 4 days, each day consisting of 4 equal meals
  • On day 5, subjects received Big Mac Attack lunch consisting of Big Mac, french fries and milk shake

Control Variables


Description of Actual Data Sample:

Initial N: 5 nonobese type 1 diabetic subjects

Attrition (final N):  5, 4 males, 1 female

Age:  range 24 - 51 years

Ethnicity:  not mentioned

Other relevant demographics:


Location: Massachusetts


Summary of Results:

Other Findings

The mean 24-hour insulin requirements to maintain normoglycemia was greater for the 60% carbohydrate diet than the 40% diet.

Although the 4 meals were of equal size, in all patients the insulin required to cover breakfast > lunch > dinner > snack.

Expressed as milliunits per kcal, the amount of insulin to cover breakfast was greater than the 60% (P < 0.05) than the 40% carbohydrate diet and greater for breakfast than the other meals (P < 0.01).

Insulin requirements for the Big Mac meal (43% carbohydrate) were 58% greater than for the 40% carbohydrate diet, even after correction for caloric differences.

Author Conclusion:
In summary, insulin requirements in type 1 diabetic patients depend on the carbohydrate content of their diet and are greater in the morning than later in the day even when meal size is constant.  Also, in counseling for the type 1 diabetic patient, it is important to emphasize the difficulty in estimating the change in insulin required for very large meals, especially if they are high in fat and carbohydrates.
Funding Source:
Government: NIH,
University/Hospital: Joslin Diabetes Center, Brigham and Women's Hospital, Harvard Medical School
Foundation associated with industry:
Reviewer Comments:
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? N/A
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) N/A
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? N/A
  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%.) Yes
  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? 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.) 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? Yes
  6.6. Were extra or unplanned treatments described? Yes
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? N/A
  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)? N/A
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? N/A
  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? 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