DM: Types of Fat (2014)

Delahanty LM, Nathan DM, Lachin JM, Hu FB, Cleary PA, Ziegler GK, Wylie-Rosett J, Wexler DJ, Diabetes Control and Complications Trial/Epidemiology of Diabetes. Association of diet with glycated hemoglobin during intensive treatment of type 1 diabetes in the Diabetes Control and Complications Trial. Am J Clin Nutr. 2009; 89 (2): 518-524.
PubMed ID: 19106241
Study Design:
Prospective Cohort Study
B - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:

The objective was to determine whether diet composition was associated with subsequent glycated hemoglobin (HbA1c) concentrations during intensive therapy for type 1 diabetes.

Inclusion Criteria:
  • Type 1 diabetes
  • Between the ages of 13 and 39 years
  • Provided written informed consent.
Exclusion Criteria:
Not described.
Description of Study Protocol:
  • Recruitment: Intensively treated participants were part of the Diabetes Control and Complications Trial (DCCT)
  • Design: Prospective cohort study
  • Blinding used: Implied with measurements.


Intensive treatment: Goal was to achieve HbA1c concentrations as close as safely possible to the non-diabetic range (less than 6.05%), these concentrations were achieved with either continuous subcutaneous insulin infusion or multiple daily injections of insulin guided by frequent (more than four times per day) self-monitoring of blood glucose. The Intensive Treatment Group also received dietary, behavioral and exercise counseling.

Statistical Analysis

  • Normal error linear models adjusted for age and sex were used to assess the association of covariates with the mean concentrations of HbA1c with each modeled with quantiles and quantitative measures
  • Multi-variable linear regression macronutrient density models adjusted for age and sex were used to assess the relation of the macronutrient composition of diet to HbA1c at five years
  • Potential confounders were adjusted for including exercise level, serum triglyceride concentration and BMI, and finally for current insulin dose as a measure of adequate insulin and baseline HbA1c concentrations as an indicator of individual capability of achieving glycemic control or as a possible indicator of residual C-peptide production
  • All analyses were conducted by using SAS version 9.1.
Data Collection Summary:

Timing of Measurements

Measurements made over five years of follow-up.

Dependent Variables

  • Glycated hemoglobin (HbA1c): Measured at a central laboratory and the primary outcome variable was HbA1c value at Year Five
  • Fasting serum lipid concentrations were measured quarterly and height and weight were used to calculate BMI.

Independent Variables

Intensive treatment: Goal was to achieve HbA1c concentrations as close as safely possible to the non-diabetic range (under 6.05%). These concentrations were achieved with either continuous subcutaneous insulin infusion or multiple daily injections of insulin guided by frequent (more than four times per day) self-monitoring of blood glucose. The Intensive Treatment Group also received dietary, behavioral and exercise counseling.
  • Trained dietitians collected a modified Burke-type diet history at study entry, at two and five years and at the end of the study
  • Before the interview, DCCT participants or their family members completed a Food Pattern Questionnaire and a Food Preparation Questionnaire that listed all foods consumed at least twice per month
  • Exercise levels were recorded at each annual visit and coded as "strenous" or at least five hours of very hard exercise per week or vigorous (occupation regarding some physical activity and at least five hours of hard or very hard exercise or at least eight hours of hard or very hard exercise), "moderate" (occupation requiring some physical activity or at least five hours of moderate exercise) or "sedentary" (sedentary occupation and at least five hours of exercise per week)
  • Insulin dose in units per kilogram per day was available yearly but this value was missing for a few patients.
Description of Actual Data Sample:
  • Initial N: 532 participants
  • Attrition (final N): 532 (52% women)
  • Age: Mean age of 27±7 years (range, 13 to 39)
  • Ethnicity: Not described
  • Other relevant demographics: HbA1c at baseline, 9.12±1.57%
  • Anthropometrics: Baseline BMI, 23.2±2.7kg/m2
  • Location: Boston, MA.
Summary of Results:

Key Findings

  • Mean carbohydrate intake was 45.5% of energy, while total fat contributed 36.8%, saturated fat contributed 12.7%, monounsaturated fat contributed 13.9% and polyunsaturated fat contributed 7.5% of energy, respectively.
  • Although total calorie intake decreased, BMI increased because of decreased catabolism with improved control of diabetes.
  • Higher insulin dose (P<0.0001), lower carbohydrate intake (P=0.01), and higher saturated (P=0.002), monounsaturated (P=0.02) and total fat (P=0.004) intakes were significantly associated with higher HbA1c concentrations at year 5.
  • In age- and sex-adjusted multivariate macronutrient models, substitution of fat for carbohydrate was associated with higher HbA1c concentrations (P=0.01), which remained significant after adjustment for exercise level, serum triglycerides, and BMI (P=0.02) but was no longer significant (P=0.1) after adjustment for baseline HbA1c and concurrent insulin dose. 


Author Conclusion:
  • The results from this study support current recommendations regarding the limitation of saturated fat intake while promoting the consumption of nutrient-dense carbohydrates, such as fruit, whole grains and vegetables with appropriate insulin doses as needed
  • Future research needs to explore whether persons with diabetes inadvertently increase their saturated fat intake in their efforts to control carbohydrate intake and glycemia.
Funding Source:
Government: NIH Career Development award K23 DK080228
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? No
  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? 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? Yes
  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? 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? 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)? 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? 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