AWM: Low Carbohydrate Diet (2006)
Subjects volunteered for study.
Randomized Crossover Trial.
Blinding used (if applicable)
Intervention (if applicable)
Subjects consumed a very-low-carbohydrate diet and a low-fat diet for 2 consecutive 6-week periods.
One-way repeated measures ANOVA was used to evaluate changes over time for all variables. Significant main effects were analyzed further using Fisher least significant difference post-hoc test. Normalized inflammatory biomarkers analyzed with paired Student's t tests.
Timing of Measurements
Subjects consumed 2 weight loss diets for 2 consecutive 6-week periods. Fasting blood samples taken at baseline and after each diet.
- Blood samples measured for high-sensitivity IL-6, high-sensitivity TNF-alpha, soluble ICAM-1, soluble P-selectin and high-sensitivity CRP, and determined using ELISA
- Very-low-carbohydrate (<10% kcals from carbohydrate, 30% protein, 60% fat) or low-fat diet (20% protein, 25% fat and 55% carbohydrate), both designed to be hypoenergetic (-2.1 MJ/day). Energy levels based on nearest 837 kJ increment based on REE obtained with indirect calorimetry. Dietary compliance checked for urinary reagent strips when in ketosis during very-low-carbohydrate diet. Analysis performed on 7 days of diet records at baseline and 21 days during the experimental periods.
Initial N: 15 men
Attrition (final N): 15 men
Age: 33.2 +/- 11.3 years
Ethnicity: Not mentioned.
Other relevant demographics: Body mass: 109.1 +/- 17.8 kg, body fat: 34.9 +/- 5.2%, BMI 34.3 +/- 5.6
Location: University of Connecticut
|10.86 +/- 2.47||7.77 +/- 1.81||6.54 +/- 1.19|
16 +/- 2
28 +/- 5
20 +/- 4
|Carbs %||47 +/- 5||8 +/- 3||56 +/- 7|
35 +/- 4
63 +/- 4
23 +/- 7
Both the very-low carbohydrate diet and low-fat diet resulted in significant decreases in body mass (-6.5 +/- 3.0 kg, P < 0.01, and -3.7 +/- 3.3 kg, P < 0.01, respectively). There was no order effect as to which diet the subject was initially randomized to.
The low carbohydrate diet was significantly different from the low-fat diet for energy, protein, carbohydrate, total fat, saturated fat, polyunsaturated fat and cholesterol (P < 0.05).
Both the low-fat and the very-low carbohydrate diets resulted in significant decreases in absolute concentrations of high-sensitivity tumor necrosis factor-alpha, high-sensitivity interleukin-6, high-sensitivity C-reactive protein, and soluble intercellular cell-adhesion molecule-1.
There was no significant change in absolute soluble P-selectin concentrations after either diet.
Normalized inflammatory values represented as the delta change per 1 kg reduction in body mass showed a significant difference between the 2 diets only for soluble P-selectin (P < 0.05).
Quality Criteria Checklist: Primary Research
|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|
|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?||???|
|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?||???|
|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?||No|
|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.)||No|
|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|