EAL

PDM: Metabolic Syndrome (2013)

Citation:

Al Sarraj T, Saadi H, Volek JS, Fernandez ML. Carbohydrate restriction favorably alters lipoprotein metabolism in Emirati subjects classified with the metabolic syndrome. Nutr Metab Cardiovasc Dis 2010;20(10):720-6.

PubMed ID: 19748249

Study Design:

Randomized Controlled Trial

Class:

A - Click here for explanation of classification scheme.

Quality Rating:

POSITIVE: See Quality Criteria Checklist below.

Research Purpose:

The purpose of this study was to evaluate the effects of a carbohydrate-restricted diet (CRD) and a low-fat diet supported by the American Heart Association on plasma lipoprotein cholesterol, lipoprotein subfractions, and apolipoprotein concentrations among Emirati adults classified with Metabolic syndrome (MetS). The hypothesis was that reduction in dietary carbohydrates would yield a less atherogenic lipoprotein profile compared to the AHA diet.

Inclusion Criteria:

All subjects signed an informed consent form written in Arabic before participating in the study.
Emirati men and women aged 18-50 years diagnosed with Metabolic Syndrome using the NCEP ATP III criteria were eligible.

Exclusion Criteria:

Not described

Description of Study Protocol:

Recruitment

39 Emirati men and women aged 18-50 years diagnosed with Metabolic Syndrome were recruited from the Tawam hospital affiliated with Johns Hopkins Medicine International in the city of Al-Ain Abu Dhabi Emirate, UAE.

Design Randomized, controlled interventional trial

Blinding used: implied with measurements

Intervention:

Subjects were either randomized to a carbohydrate restricted diet (CRD) group with an energy distribution of 20-25% carbohydrate, 25-30% protein and 45-50% fat for 12 weeks or to a combination diet (a 6 week carbohydrate restricted diet followed by a 6 week conventional low-fat diet with 55% carbohydrate, 15-20% protein and <30% fat as recommended by the American Heart Association (AHA).
Both diets were prescribed to free-living subjects and no food was provided.
Registered dietitians met with subjects at baseline and every 2 weeks to counsel and educate subjects on CRD and AHA diets.
Each subject received written dietary education materials to reinforce the principles covered during the meeting session.
24-hour dietary recalls were provided by the participants every 2 weeks and were analyzed by the same dietitian who interviewed the subjects and who was familiar with the type of food consumed in the region using the Nutritional Data System 8.0.
Subjects were not asked to change their level of activity during the intervention to avoid confounding variables.

Statistical Analysis

Independent t tests were used to determine differences between total number of lipoproteins and lipoprotein cholesterol at baseline.
Repeated measures of ANOVA were used to evaluate differences across time and between dietary groups.
P < 0.05 was considered to be significant.

Data Collection Summary:

Timing of Measurements

Baseline, 6 weeks and 12 weeks.

Dependent Variables

Weight was calculated to the closest 0.2kg.
Whole body and regional body composition was assessed using a state-of the-art fan beam dual energy X-ray absorptiometry (DEXA).
Plasma lipoprotein cholesterol, lipoprotein subfractions and apolipoprotein concentrations: Apolipoproteins were measured using LINCOplex: Multiplex Biomarker Immunoassay for Luminex Instrumentation xMAP Technology.
Plasma cholesterol and triglycerides were measured by enzymatic techniques.
HDL-C was measured in human serum after precipitation of apoB containing lipoproteins.
Nuclear Magnetic Resonance was performed on 400MHz NMR analyzer. NMR quantifies >30 lipoprotein subclasses that are empirically grouped into 9 smaller subclasses based on particle diameters: large VLDL (35-60nm), medium VLDL (27-35nm), small VLDL (23-27nm), large LDL (21.2-23nm), medium LDL (19.8-21.2), small LDL (18-19.8nm), and small HDL (7.3-8.2nm).
Weighted average lipoprotein particle sizes in diameters were calculated based on the diameter of each lipoprotein subclass multiplied by its respective relative concentration.

Independent Variables

Subjects were either randomized to a carbohydrate restricted diet (CRD) group with an energy distribution of 20-25% carbohydrate, 25-30% protein and 45-50% fat for 12 weeks or to a combination diet (a 6 week carbohydrate restricted diet followed by a 6 week conventional low-fat diet with 55% carbohydrate, 15-20% protein and <30% fat as recommended by the American Heart Association (AHA).
Both diets were prescribed to free-living subjects and no food was provided.
Registered dietitians met with subjects at baseline and every 2 weeks to counsel and educate subjects on CRD and AHA diets.
Each subject received written dietary education materials to reinforce the principles covered during the meeting session.
24-hour dietary recalls were provided by the participants every 2 weeks and were analyzed by the same dietitian who interviewed the subjects and who was familiar with the type of food consumed in the region using the Nutritional Data System 8.0.
Subjects were not asked to change their level of activity during the intervention to avoid confounding variables.

Description of Actual Data Sample:

Initial N:39 men and women

Attrition (final N): 39 men and women (15 men/24 women), 20 in the CRD group, 19 in AHA group

Age: Range 18-50 years

Ethnicity:Emirati

Other relevant demographics:Not reported

Anthropometrics: No significant differences between groups at baseline

Location:Tawam hospital, Al-Ain, Abu Dhabi Emirate, UAE

Summary of Results:

Key Findings

All subjects reduced body weight, LDL cholesterol and triglycerides (P<0.01).
At baseline all subjects had low concentrations of medium VLDL and total HDL particles associated with the very low plasma triglycerides and HDL cholesterol in this population.
After 12 weeks, the large VLDL subfractions were decreased over time for subjects in the CRD group (P<0.01), while these changes were not observed in those subjects who changed to the AHA diet.
The number of medium and small HDL particles decreased for all subjects rendering a less atherogenic lipoprotein profile.
In agreement with these results, a significant decrease in apolipoprotein B (apoB) was observed (P<0.01).
The medium HDL subfraction and apo A-II which can be considered pro-atherogenic were also decreased over time in the CRD group only.

Author Conclusion:

The results of this study show that carbohydrate restriction modifies CVD risk factors in Emirati subjects with MetS by decreasing the number of atherogenic lipoproteins.

Funding Source:

Government:

Health Authority for the Emirate of Abu Dhabi (HAAD)

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?	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.)	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?	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