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DM: Types of Fat (2014)

Citation:

Strychar IS, Cohn JS, Renier G, Rivard M, Aris-Jilwan N, Beauregard H, Meltzer S, Belanger A, Dumas R, Ishac A, Radwan F, Yale J-F: Effects of a diet higher in carbohydrate/lower in fat versus lower in carbohydrate/higher in monounsaturated fat on postmeal triglyceride concentrations and other cardiovascular risk factors in type 1 diabetes. Diabetes Care, 2009; 32: 1,597-1,599.

PubMed ID: 19542011
 
Study Design:
Randomized Controlled Trial
Class:
A - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:

To compare the effects of a eucaloric diet higher in carbohydrates and lower in fat vs. lower in carbohydrates and higher in monounsaturated fat on post-meal triglyceride (TG) concentrations and other cardiovascular disease risk factors in non-obese subjects with type 1 diabetes and in good glycemic control.

Inclusion Criteria:
  • Adults with type 1 diabetes on intensive insulin therapy
  • Provided written informed consent.
Exclusion Criteria:
  • Body mass index (BMI): ≥30kg/m2
  • Hemoglobin: A1C>8.4%
  • Major diabetes complications.
Description of Study Protocol:
  • Recruitment: Adults with type 1 diabetes on intensive insulin therapy were recruited
  • Design: Randomized controlled trial
  • Blinding used: Implied with measurements.

Intervention

Subjects were randomized to one of two diets for six months:

  1. High carbohydrate, low-fat diet: 54% to 57% carbohydrate, 27% to 30% fat and 10% monounsaturated fat
  2. Low carbohydrate, high monounsaturated fat diet: 43% to 46% carbohydrates, 37% to 40% total fat, 20% monounsaturated fat
Meals were standardized according to diet assignment: Breakfast and lunch were similar for the two groups and differences in carbohydrate/fat contents were achieved at the supper meal. The lower-carbohydrate, higher monounsaturated fat diet had fewer starch choices and more fat choices in the form of olive oil. Usual prescribed insulin doses were given and took into account premeal glycemia and carbohydrate meal content.

Statistical Analysis

  • Mann-Whitney tests were used to compare values between the two diets
  • Wilcoxon's signed-rank tests were used to compare values within each diet group since many variables did not meet the normality assumption of the T-test
  • Significance was set as P≤0.05.
Data Collection Summary:

Timing of Measurements

Measurements made at baseline and six months.

Dependent Variables

Methods for measurement were not described
  • BMI
  • Blood pressure
  • A1C
  • Plasma lipids
  • Adhesion molecules
  • Postmeal triglyceride (TG) concentrations
  • Markers of oxidation, thrombosis and inflammation.

Independent Variables

  • Subjects were randomized to one of two diets for six months:
    1. High carbohydrate, low-fat diet: 54% to 57% carbohydrate, 27% to 30% fat and 10% monounsaturated fat
    2. Low carbohydrate, high monounsaturated fat diet: 43% to 46% carbohydrates, 37% to 40% total fat, 20% monounsaturated fat
  • Meals were standardized according to diet assignment: Breakfast and lunch were similar for the two groups and differences in carbohydrate and fat contents were achieved at the supper meal
  • Usual prescribed insulin doses were given and took into account premeal glycemia and carbohydrate meal content
  • On a weekly basis, a dietitian monitored subjects' dietary intake (24-hour telephone food recall), pre-meal glycemia, dietary carbohydrate meal content and insulin doses administered
  • Subjects recorded daily glycemic levels, insulin doses, grams of meal-time carbohydrates and hypoglycemic events.
Description of Actual Data Sample:
  • Initial N: Assumed 30; 15 in each group
  • Attrition (final N): 30 subjects; gender not reported
  • Age: Mean, 37.9±8.1 years
  • Ethnicity: Not described
  • Other relevant demographics: Years since diagnosis, 16.5±10.6
Anthropometrics
  • Mean BMI: 24.3±2.6kg/m2
  • Baseline characteristics were similar between the two study groups
  • Baseline A1C was 7.3±0.7% in the Higher-Carbohydrate/Lower-Fat Diet Group and 7.0±0.7% in the Lower-Carbohydrate/Higher-Monounsaturated Fat Diet Group
  • Location: Quebec, Canada.
Summary of Results:

Key Findings

  • There were no significant differences between groups other than decreased plasminogen activator inhibitor 1 (PAI-1) levels and weight gain in the Lower Carbohydrate/Higher-Monounsaturated Fat Group
  • There was a small but statistically significant weight gain of 1.6±1.8kg (P<0.05) in the Lower Carbohydrate/Higher-Monounsaturated Fat Group, however there were no significant differences between groups in terms of A1C, total cholesterol, HDL-cholesterol, LDL-cholesterol, triglycerides or blood pressure
  • In addition, there were no differences between groups for insulin doses
  • During the 24-hour testing, the Lower-Carbohydrate/Higher-Monounsaturated Fat Group had a lower plasma TG profile.
Author Conclusion:

In conclusion, a diet lower in carbohydrate and higher in monounsaturated fat is an appropriate nutrition therapy for type 1 diabetic individuals with good metabolic and weight control.

Funding Source:
Government: Canadian Institutes of Health Research, Institute of Nutrition and Metabolism, Ottawa Canada
Reviewer Comments:
  • Methods for measurement of outcomes were not described
  • Small sample size and sample not well described
  • Relatively short study duration.
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? No
  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? 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? 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? ???
  7.5. Was the measurement of effect at an appropriate level of precision? ???
  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? No
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