PDM: Metabolic Syndrome (2013)


Mestek ML, Plaisance EP, Ratcliff LA, Taylor JK, Wee SO, Grandjean PW. Aerobic exercise and postprandial lipemia in men with the metabolic syndrome. Med Sci Sports Exerc. 2008; 40(12): 2,105-2,111.

PubMed ID: 18981938
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 compare the respective effects of single sessions of aerobic exercise requiring 500kcal of caloric expenditure performed at low- vs. moderate-intensity and in a continuous vs. accumulated pattern on post-prandial lipemia.

Inclusion Criteria:

Physically inactive (not meeting U.S. Surgeon General's physical activity recommendations for at least six months prior to study) males with metabolic syndrome as defined by NCEP ATP III.

Exclusion Criteria:
  • Any known cardiovascular, pulmonary or metabolic diseases
  • Taking prescription medications that alter lipid or carbohydrate metabolism.
Description of Study Protocol:


  • Participants completed a control condition consisting of a high-fat meal and blood sampling at two-hour intervals for six hours, followed by three aerobic exercise conditions completed in a randomized order:
    • A continuous moderate-intensity exercise
    • A continuous low-intensity exercise
    • Two accumulated moderate-intensity sessions
  • The test meal and blood sampling were repeated 12 to 14 hours after exercise.

Blinding Used 

Implied with measurements.


Continuous moderate-intensity exercise (60% to 70% of VO2peak), continuous low-intensity exercise (35% to 45% of VO2peak) and two accumulated moderate-intensity exercise sessions (60% to 70% of VO2peak).

Statistical Analysis

Data analysis was completed with SAS for Windows, version 9.1. 

Data Collection Summary:

Timing of Measurements

Four experimental sessions were conducted on each participant. At each session, the participant completed a control condition of a high-fat meal and blood sampling at two-hour intervals for proceeding six hours, followed by a bout of exercise (continuous moderate-intensity exercise, continuous low-intensity exercise and two accumulated moderate-intensity exercise sessions). The test meal and sampling were conducted 12 to 14 hours post-exercise.

Dependent Variables

  • Body composition:
    • Height (stadiometer)
    • Weight (calibrated balance scale)
    • Body mass index (BMI)
    • Waist circumference (narrowest portion of torso above the umbilicus and below the xiphoid process of sternum)
    • Body composition (DEXA)
  • Graded exercise testing: Oxygen consumption (breath-by-breath analysis)
  • Blood markers:
    • Hemoglobin concentrations and hematocrit values (from whole blood samples, serum triglycerides (enzymatic reagent)
    • Glucose (glucose oxidase)
    • Insulin (human insulin-specific radioimmunoassay kit.

Independent Variables

  • Control condition consisting of a high-fat meal and blood sampling
  • Continuous moderate-intensity exercise (60% to 70% of VO2peak)
  • Continuous low-intensity exercise (35% to 45% of VO2peak)
  • Two accumulated moderate-intensity exercise sessions (60% to 70% of VO2peak).
Description of Actual Data Sample:
  • Initial N: 14 males
  • Attrition (final N): 14
  • Age: 34 to 52 years old
  • Other relevant demographics: Presented with metabolic syndrome
  • Anthropometrics:  Subjects served as own control in crossover design
  • Location: Boulder, CO, US.
Summary of Results:

Key Findings

Variable Pre-exercise Post-exercise P-value
Triglyceride (mg per dL) 204±11 207±11 0.74
HDL (mg per dL) 48±8 48±7 0.42
Insulin (μU per ml) 22.9±1.7 23.8±1.7 0.92
Glucose (mg per dL) 104±1.3 105±1.3 0.26
HOMA score 6.0±0.5 6.3±0.5 0.40
Glucose:insulin ratio 4.5±0.8 5.6±0.4 0.64

Other Findings

  • Body weight did not differ over the course of the study protocol (P=0.59)
  • Analysis of dietary records indicated no significant differences in total caloric intake or major macronutrient content among any of the study conditions
  • The TG AUC decreased by 27% after continuous low-intensity exercise
  • TG concentrations were also reduced by 22% and 21% at four-hour post-meal after continuous low-intensity exercise and continuous moderate-intensity exercise, yet TG parameters were no different from the control condition after two accumulated moderate-intensity sessions (P<0.05 for all).
Author Conclusion:

The authors concluded that this is the first study to demonstrate that 500kcal of low-intensity exercise reduces post-prandial lipemia in men with metabolic syndrome as effectively as moderate-intensity exercise and that even low-intensity exercise appears to be as effective as moderate-intensity exercise in reducing post-prandial lipemia in men with metabolic syndrome.

Funding Source:
University/Hospital: University of Colorado, Boulder, Integrative Vascular Biology Laboratory
Reviewer Comments:

Inclusion/exclusion criteria and recruitment methods were not described. Small sample size, only men were studied.

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? ???
  2.2. Were criteria applied equally to all study groups? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? ???
  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? 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? 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)? 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? 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