MNT: Weight Management (2015)


Goulet J, Lamarche B, Charest A, Nadeau G, Lapointe A, Desroches S, Lemieux S. Effect of a nutritional intervention promoting the Mediterranean food pattern on electrophoretic characteristics of low-density lipoprotein particles in healthy women from the Quebec City metropolitan area. Br J Nutr. 2004; 92 (2): 285-293.

PubMed ID: 15333160
Study Design:
Non-Controlled Trial
D - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:
To study the impact of a nutritional intervention promoting the Mediterranean food pattern in free-living conditions on LDL peak particle diameter (LDL-PPD).
Inclusion Criteria:
  • Age, 30 years to 65 years
  • Free from metabolic disorders requiring treatment
  • Stable body weight for at least three months before the start of the study
  • In charge of food purchases and meal preparation most of the time
  • Diet consistent with the usual Canadian food pattern
  • Mediterranean diet score less than 27.
Exclusion Criteria:
  • Aged under 30 years or over 65 years
  • Metabolic disorder requiring treatment
  • Unstable body weight
  • Not in charge of food purchases and meal preparation most of the time
  • Diet not consistent with the usual Canadian food pattern
  • Mediterranean diet score of 27 or more.
Description of Study Protocol:


Participants were recruited through the Laval University newspaper during the summer of 2001.


  • This non-controlled trial consisted of a 12-week nutrition intervention during which participants attended two group sessions and three individual sessions with a registered dietitian
  • Dietary intake, anthropometrics and plasma lipid profiles were assessed at zero, six and 12 weeks
  • The intervention was conducted over two phases
  • For data analysis, the sample was divided on the basis of baseline LDL-PPD, using tertiles of the distribution (258.4 Å and 260.0 A). 


  • The nutrition intervention included two group sessions. The first group session provided information on the Mediterranean food pattern; the second group session, conducted at four weeks after the beginning of the intervention, was a cooking lesson.
  • Individual sessions with a registered dietitian took place during Weeks One, Six and 12. During these sessions, the dietitian used food frequency questionnaires (FFQ) and the Mediterranean food pyramid to identify goals and personalize dietary changes for each participant.
  • Unannounced 24-hour recalls were performed by telephone at Weeks Two, Four, Eight and 10 to provide support and reinforce key principles of the Mediterranean diet. 

Statistical Analysis

  • Data were compared using ANOVA for repeated measures to identify time effects. In the presence of significant time effects, contrast analyses were used to determine the location of differences.
  • Terms reflecting the potential phase-effect were systematically entered in each model to account for potential interaction with the treatment effect
  • Spearman correlations were computed to quantify associations among parametric and non-parametric variables
  • Partial Spearman correlations were performed between changes in LDL-electrophoretic characteristics and changes in dietary score to partial out the effect of anthropometric changes
  • Triglycerides were not normally distributed and analyses were performed on log-transformed values. The dietary variables were log-transformed when necessary to obtain a normal distribution.
  • The intervention effect within each tertile and the interaction between time and baseline characteristics were calculated by ANOVA. In the presence of significant effects, contrast analyses were performed.
Data Collection Summary:

Timing of Measurements

Dietary intake, anthropometrics and plasma lipid profiles were assessed at zero, six and 12 weeks. 

Dependent Variables

  • BMI
  • Waist circumference
  • Total cholesterol
  • Triglycerides
  • Apo B
  • HDL-cholesterol
  • LDL-cholesterol
  • LDL peak particle size (obtained by 2% to 16% polyacrylamide gel electrophoresis of whole plasma)
  • Dietary intake (three-day food records)
  • Mediterranean dietary score (food frequency questionnaire).

Independent Variables

Nutritional intervention.

Control Variables

Three dietitians were trained to provide a standardized intervention.

Description of Actual Data Sample:
  • Initial N: 77 (77 females, no males)
  • Attrition (final N): 71 (8% drop-out rate)
  • Age: 30 years to 65 years; mean, 46.9±7.6 years
  • Ethnicity: Not described
  • Other relevant demographics: Not described.


  • BMI: 26.4±4.8kg/m2
  • Waist circumference: 850±131mm
  • When separated into tertiles based on LDL-PPD, no significant differences in age, waist circumference and BMI were observed at baseline between the three groups. Subjects with LDL-PPD more than 260.0 Å had lower TG and higher HDL-cholesterol at baseline than the group with the lowest LDL-PPD (P<0.05). Differences between groups remained statistically significant at the end of the intervention.


Quebec City, Canada metropolitan area.
Summary of Results:

Key Findings

The intervention resulted in slight but significant improvements in anthropometrics and the metabolic profile.

  • Total cholesterol, apo B and BMI decreased slightly but significantly (P<0.01, P<0.0001 and P<0.01 respectively) at six weeks. Decreases in apo B and BMI remained statistically significant (P<0.05 and P<0.01, respectively) at 12 weeks; total cholesterol did not.
  • Waist circumference was statistically lower at 12 weeks than at baseline (P<0.0001)
  • Among the total sample, no significant changes in LDL-cholesterol, HDL-cholesterol, TG, LDL-PPD, LDL integrated size and in LDL distribution were observed.
The intervention resulted in significant changes in dietary intakes, which were maintained throughout the 12-week study period.
  • Mediterranean score increased (P<0.0001)
  • Consumption of olive oil, fruits, vegetables, legumes, nuts and seeds, poultry and fish increased, as reflected by an increase in the individual scores for these components (P<0.001)
  • Consumption of red meat and processed meat and sweets decreased as reflected by significant increases in the individual scores for these components (P<0.0001)
  • Energy intake decreased from 8,590±2,188kJ to 7,888±1,793kJ (P<0.01)
  • Protein intake increased from 16.4±2.5g to 17.7±2.9g (P<0.01)
  • SFA intake decreased from 11.2±2.8% to 9.9±2.7% (P<0.01)
  • Cholesterol intake decreased from 280.1±139.8mg to 225.9±90.4mg (P<0.01)
  • EPA intake increased from 0.06±0.07g to 0.12±0.13g (P<0.01)
  • DHA intake increased from 0.17±0.23g to 0.27±0.36g (P<0.05)
  • MUFA:SFA ratio intake increased from 1.32±0.36 to 1.52±0.48 (P<0.01)
  • Total dietary fiber increased from 21.9±6.4g to 25.1±7.7g (P<0.01).
 Changes in LDL-PPD were associated with LDL-cholesterol values at baseline.
  • Subjects in the first tertile (LDL-PPD less than 258.4Å) showed a significant increase in LDL-PPD (P=0.03) and in the proportion of LDL percentage greater than 260Å in response to the intervention (P<0.05)
  • Subjects in the third tertile (LDL-PPD greater than 260Å) showed a significant decrease in LDL-PPD and LDL integrated size (P=0.007). LDL-PPD in this group remained statistically higher than in the first two tertiles at the end of the intervention (P<0.0001).

Other Findings

  • Increases in the Mediterranean score were significantly associated with decreases in LDL-cholesterol concentrations (P=0.04)
  • Decrease in sweets consumption was significantly associated with a decrease in LDL-PPD (P=0.02).
Author Conclusion:
  • A nutritional intervention promoting the Mediterranean food pattern in free-living conditions was effective in modifying the food habits of healthy women from the Quebec City metropolitan area
  • These changes in the food pattern were associated with only marginal variations in LDL electrophoretic characteristics. However, even in a group of healthy women, those in the risk category based on their LDL-PPD experienced significant and beneficial changes in their LDL size phenotype.
  • These subtle changes in their LDL particle size and in cholesterol distribution among various LDL subfractions may explain part of the cardiovascular benefits that have been attributed to the Mediterranean diet in subjects at increased CHD risk.
Funding Source:
Government: Canada Research Chair in Nutrition, Functional Foods and Cardiovascular Health
Reviewer Comments:
No control group.
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) 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.) 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? 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? 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)? 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