EAL

AWM: Low Carbohydrate Diet (2006)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To test the hypothesis of whether an isocaloric diet lower in total carbohydrates and higher in protein and monounsaturated fat would have a more favorable effect on weight loss than the NCEP Step II diet.

Inclusion Criteria:

Age older than 18 years, BMI of 27+, willingness and stated ability to adhere to a prescribed diet for 3 months at home without alteration in physical activity.

Exclusion Criteria:

History of thyroid disease or IDDM, pregnancy, unstable medical condition, and current use of oral or parenteral corticosteroids, testosterone, appetite suppressants, or other medications known to affect weight or appetite.

Description of Study Protocol:

Recruitment

Recruited by media announcements.

Design

Randomized Controlled Trial. Randomization done using a block design by sex to achieve equal sex distribution.

Blinding used (if applicable)

All anthropometric measurements obtained by observer blinded to treatment assignment.

Intervention (if applicable)

Enrolled to follow NCEP diet or MLC diet for 12 weeks.

Statistical Analysis

Size of sample chosen to provide more than 90% power to detect a 10 lb difference between groups. For significance of differences between groups, t test for continuous variables and chi-square tests for discrete variables were used. Triglyceride values were log transformed. For discrete variables in which the sample size was 5 or less, the Fisher exact test was used.

Data Collection Summary:

Timing of Measurements

Follow-up visits for diet counseling and anthropometric measurements occurred every 2 weeks for 12 weeks.

Dependent Variables

Weight measured with infoor clothing and without shoes on a single scale
Height measured with all subjects standing erect without shoes using same vertical rod
Hip girth measured at the largest horizontal circumference around the buttocks
Waist girth measured at narrowest circumference viewed from the front
Fasting blood samples analyzed for total, HDL cholesterol, triglycerides, LDL cholesterol

Independent Variables

NCEP diet (1300 kcal for women, 1600 kcal for men, 55% kcals from carbohydrate, 30% from fat, 15% from protein) or MLC diet (1300 kcal for women, 1600 kcal for men, phase 1 of 2 weeks of 10% kcals from carbohydrate, 28% from protein, 62% fat, phase 2 of 2 weeks of 27% from carbohydrates, 30% from protein, 43% from fat, and phase 3 of 8 weeks of 28% from carbohydrate, 33% from protein, 39% from fat). RD and NP instructed participants about diet for 1 hour at first visit, 30 minutes thereafter. RD assessed appropriateness of foods through 24 hour recalls but actual food intake was not quantified.

Control Variables

Description of Actual Data Sample:

Initial N: 60 participants, 29 women, 31 men

Attrition (final N): 54 participants completed trial, 25 in NCEP, 29 in MLC. Of 6 dropouts, 5 were in NCEP, 1 in MLC. Authors note that this may be due to lack of weight loss or dissatisfaction with diet.

Age: Aged 27 - 71 years, mean age 44 in NCEP group and 46 in MLC group

Ethnicity: Not mentioned

Other relevant demographics: NCEP BMI: 35.5 +/- 6.0, MLC BMI: 34.9 +/- 4.0

Anthropometrics: At baseline, there were no significant differences between groups with respect to age, weight, BMI, waist-to-hip ratio, and any lipid variables.

Location: Florida

Summary of Results:

	MLC (n=22)	NCEP (n=23)	P-value between groups
Weight, lbs	-13.6 +/- 4.0	-7.5 +/- 4.4	0.02
Waist-to-hip ratio	-0.02 +/- 3.82	-0.01 +/- 3.47	0.27
Total cholesterol, mg/dl	-11.9 +/- 29.2	-13.3 +/- 17.5	0.83
HDL cholesterol, mg/dl	-1.3 +/- 9.4	-3.8 +/- 6.3	0.27
LDL cholesterol, mg/dl	-3.9 +/- 27.4	-6.4 +/- 15.6	0.68
Triglycerides, mg/dl	-42.0 +/- 101.3	-15.3 +/- 46.2	0.12
Total/HDL cholesterol	0.13 +/- 0.91	-0.07 +/- 0.59	0.36
LDL particle size peak, nm	4.8 +/- 6.3	1.2 +/- 4.3	0.41
Percentage of dense LDL	-6.1 +/- 12.4	-1.4 +/- 6.1	0.17

Other Findings

Weight loss was significantly greater in the MLC (13.6 lbs) than in the NCEP group (7.5 lbs), a difference of 6.1 lb (P = 0.02).

There were no significant differences between the groups for total, LDL and HDL cholesterol, triglycerides, or the proportion of small dense LDL particles.

There were significantly favorable changes in all lipid levels within the MLC but not within the NCEP group.

Waist-to-hip ratio was not significantly reduced between the groups (P = 0.27), but it significantly decreased within the MLC group (P = 0.009).

Author Conclusion:

Compared with the NCEP diet, the MLC diet, which is lower in total carbohydrates but higher in complex carbohydrates, protein and monounsaturated fat, caused significantly greater weight loss over 12 weeks. There were no significant differences between the groups in blood lipid levels, but favorable changes were observed within the MLC diet group.

Funding Source:

Not-for-profit

Reviewer Comments:

Actual food intake not measured although compliance was monitored.

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?	???
	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?	Yes
	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