PDM: Metabolic Syndrome (2013)


Klemsdal TO, Holme I, Nerland H, Pedersen TR, Tonstad S. Effects of a low glycemic load diet vs. a low-fat diet in subjects with and without the metabolic syndrome. Nutr Metab Cardiovasc Dis. 2010; 20 (3): 195-201.

PubMed ID: 19502017
Study Design:
Randomized Controlled Trial
A - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:

The aim of the study was to compare the one-year clinical effects of a low-glycemic load (LGL) diet vs. a low-fat diet in a trial with a moderately intense dietary intervention in subjects with varying degrees of metabolic syndrome.

Inclusion Criteria:
  • BMI between 28 and 40kg/m2 for men
  • BMI between 28 and 35kg/m2 for women
  • Have at least one criterion of the metabolic syndrome as defined by the National Cholesterol Education Program in 2001
  • All subjects signed a written informed consent
  • The patients were not offered any economical compensation.
Exclusion Criteria:
  • Any symptomatic cardiovascular disease and diabetes requiring medication
  • Patients taking lipid-lowering treatment or weight reducing medication within 12 weeks were also excluded
  • Subjects with eating disorders were excluded by history.
Description of Study Protocol:


  • 202 subjects were randomized
  • 128 subjects were recruited through newspaper advertisement, 27 among the regular patients at the clinic, eight from the screening of new patients at the clinic and 38 from other sources.


Randomized controlled trial.

Blinding Used

Implied with measurements.


  • Low-glycemic load (LGL) diet (35% to 40% of energy from fat, 25% to 30% energy from protein, 30% to 35% from carbohydrates and up to 3% from alcohol)
  • Low-fat diet (less than 30% of energy from fat, about 15% from protein, 55% to 60% from carbohydrates and up to 3% from alcohol).

Statistical Analysis

  • Repeated measure ANOVA used to assess the group differences
  • A regression analysis of a possible interaction between the presence of the metabolic syndrome and the effect of the randomized diets on the major clinical end-points were performed
  • All analyses were performed using the statistical software SPSS, version 14.0.
Data Collection Summary:

Timing of Measurements

Measurements made at baseline, three months and one year.

Dependent Variables

  • Change in body weight and change in waist/hip circumference. Waist circumference was measured in mid-exhalation midway between the lower rib margin and the iliac crest, and hip circumference was measured at the levels of the trochanters through the pubic symphysis.
  • Blood pressure and heart rate measured using an automatic device and performed after the subject had rested in the sitting position for five minutes
  • Change in glucose, high sensitive CRP, total cholesterol, HDL cholesterol, triacylglcyerol and apolipoprotein B were measured with standardized methods at the Department of Clinical Chemistry Ullevaal University Hospital, Oslo. Analyses of C-peptide and insulin were performed at the Hormone laboratory at Aker University Hospital, Oslo.

Independent Variables

  • Low glycemic load diet (LGL): Target dietary intake was 35-40% of energy from fat, 25-30% from protein, 30-35% from carbohydrates and up to 3% from alcohol
  • Low-fat diet: Goal was to achieve intake of a diet with <30% of energy from fat, about 15% from protein, 55-60% from carbohydrates and up to 3% from alcohol
  • Participants in both groups were offered nine dietary counseling sessions in the course of the study (baseline, week two, months one, two, three, four, five, six and nine). The dietitian met with the subjects individually at baseline, week two, month one and month nine while all other visits with the dietitian were conducted in a group.

 Control Variables 

Description of Actual Data Sample:
  • Initial N: 320 men and women evaluated and 225 screened. 202 men and women were randomized.
  • Attrition (final N): At one year
    • 78 of 100 subjects in the LGL group
    • 86 of 102 subjects in the low-fat group completed the study
  • Age: 30-65 years
    • Mean age 50.1 in the LDL group
    • 49.9 in the low-fat diet group
  • Ethnicity: Caucasian
  • Other relevant demographics:
  • Anthropometrics: Baseline characteristics were similar between the low glycemic load and low-fat groups
  • Location: Norway.


Summary of Results:

Key Findings

  • The achieved differences in macronutrient intakes between the groups were highly significant for all macronutrients
  • The LGL group consumed significantly less bread (96±52 grams per day vs. 124±54 grams per day, P=0.001), potatoes (4±11 grams per day vs. 14±30 grams per day, P=0.007), rice (3±6 grams per day vs. 6±7 grams per day, P=0.009) and slightly less pasta (4±7 grams per day vs. 5±8 grams per day, P=0.21)
  • The LGL group tended to experience a greater weight loss at three and six months than the low-fat group (-4.8±3.9kg vs. -3.8kg±3.5, P=0.06 and -5.7±4.9kg vs. -4.8±5.7kg, P=0.25) however, the opposite trend was observed after one year (-4.0kg vs. -4.3kg, P=0.69)
  • The proportion of patients with the metabolic syndrome (at least three criteria) was reduced significantly (P<0.001) in both groups, from 65% to 45% in the LGL group and from 60% to 42% in the low-fat group, with no significant differences between groups
  • At one year the change in waist circumference and waist-hip ratio were significantly greater in subjects in the low-fat compared to the LGL diet group (-5.8cm vs. -4.1cm, P=0.03, and -0.03 vs. -0.01, P=0.09)
  • There was a significant interaction between the presence of the metabolic syndrome and the effect of the two diets on waist circumference, with a less favorable effect of the LGL diet in subjects without the syndrome (P=0.039)
  • After one year, weight loss was similar in both groups (4.0±5.5 kg vs. 4.3±6.2 kg, P=NS), but waist circumference reduction was less in the low glycemic load diet group (3.9±5.3 cm vs. 5.8±6.8 cm; P=0.03).
  • In addition, after one year, there were no significant differences between groups in HDL-cholesterol, triglycerides, fasting glucose or systolic blood pressure, however, diastolic blood pressure decreased more significantly in the low glycemic load diet group (-4.0 ± 8.7 mmHg vs. -1.1 ± 8.5 mmHg, P=0.02).
  • Renal outcomes were not reported.



Author Conclusion:

After 12 months, both diets reduced body weight and the metabolic disturbances similarly, but the LGL diet appeared more suitable for subjects with the metabolic syndrome, and was less effective in those without it. The results from this study suggest that individualization of dietary advice according to the metabolic profile of the patient could enhance the clinical responses.

Funding Source:
Government: Grant #NCT00230919 from the Norwegian National Research Council
Reviewer Comments:

This trial demonstrated that clinically significant improvements in body weight and several risk factors including characteristics of metabolic syndrome can be achieved and maintained for one year with both an LGL diet and a more conventional low-fat diet. The major strength of the trial was its completion rate, which was above that observed in most earlier trials.

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? 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) No
  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? 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? 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)? Yes
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? ???
  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? No
  9.1. Is there a discussion of findings? Yes
  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