Adult Weight Management

AWM: Low Carbohydrate Diet (2006)

Citation:

Lean MEJ, Han TS, Prvan T, Richmond PR, Avenell A.  Weight loss with high and low carbohydrate 1200 kcal diets in free living women.  Eur J Clin Nutr 1997; 51(4): 243-248.

PubMed ID: 9104574
 
Study Design:
Randomized Controlled Trial
Class:
A - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:
To examine weight loss and cardiovascular risk factors over 6 months on high and low carbohydrate diets in free living individuals.
Inclusion Criteria:
BMI > 25, free from active disease.
Exclusion Criteria:
None specifically mentioned.
Description of Study Protocol:

Recruitment

Recruitment not described.

Design

Randomized controlled trial.

Blinding used (if applicable)

Not used.

Intervention (if applicable)

Subjects assigned to 1200 kcal diets of high or low carbohydrate content.

Statistical Analysis

Paired t test was used to compare changes in measurements within each group of subjects, and independent 2 sample t tests were used to compare the differences in the changes of measurements between groups of subjects.  The rates of dropouts and differences in characteristics between treatment groups were compared by chi-square tests.  Weight loss on intention to treat was analyzed based on the last recorded weight before dropout or at study completion.  The differences in weight loss between the 23 matched pairs of postmenopausal women on high CHO or low CHO diets were tested using matched pair t tests.

Data Collection Summary:

Timing of Measurements

Subjects reviewed at 6 week intervals for 6 months.

Dependent Variables

  • Body weight and height measured with subjects wearing light clothing using regularly calibrated scales and wall mounted stadiometer
  • Waist circumference midway between the lowest rib margin and iliac crest and hip circumference at level of greater trochanters measured to nearest mm, body fat % calculated from waist circumference 
  • Serum lipids measured using standard laboratory methods 
  • Blood pressure measured with subjects lying and rested for 5 minutes recording 1st and 4th Korotkoff sounds

Independent Variables

  • 1200 kcal diets of high (58% kcals from CHO) or low (35% kcals from CHO) carbohydrate.  Dietary advice given by the same RD.  Subjects given written materials.  RD contacted subjects by telephone to reduce dropouts.

Control Variables

 

Description of Actual Data Sample:

Initial N: 110 women, 57 assigned to high CHO, 53 to low CHO

Attrition (final N):  48 of 57 (84.2%) on high CHO diet and 43 of 53 (81.1%) on low CHO diet at 3 months.  42 of 57 (73.7%) of high CHO diet and 40 of 53 (75.5%) on low CHO diet at 6 months.  

Age: High CHO:  mean 51.1 +/- 13.6 years, Low CHO: mean 50.1 +/- 14.0 years

Ethnicity:  Not described. 

Other relevant demographics:  High CHO BMI:  32.3 +/- 5.5, Low CHO BMI: 32.8 +/- 5.1

Anthropometrics:  Subgroup of 23 pairs of postmenopausal women were matched for age, postmenopausal age, and BMI.  At baseline, there were no significant differences between groups.

Location: UK

 

Summary of Results:

Other Findings

There was no difference between diet groups on rates of dropout at 3 or 6 months.

Examination at 3 months showed women on a high-carbohydrate diet lost 4.3 +/- 0.5 kg and those on a low-carbohydrate diet lost 5.6 +/- 0.6 kg of body weight.

Changes in risk factors did not significantly differ between diets throughout the study.

However, those on high carbohydrate diets significantly lowered their plasma total cholesterol by 0.33 mmol/L (95% CI: 0.10, 0.55), LDL cholesterol by 0.23 mmol/L (0.02, 0.43) and HDL cholesterol by 0.05 mmol/L (0.03, 0.10), while women on low carbohydrate diets lowered only plasma triglyceride by 0.28 mmol/L (0.08, 0.48).

Blood pressure did not change significantly on either diet.

After 6 months, women on high carbohydrate lost 5.6 +/- 0.8 kg and those on low carbohydrate lost 6.8 +/- 0.8 kg.

On the high carbohydrate diet, total cholesterol remained significantly below the baseline value at 0.34 mmol/L (0.13, 0.56), triglyceride was significantly lowered by 0.27 mmol/L (0.10, 0.45), and HDL cholesterol returned to baseline value.

On the low carbohydrate diet, triglyceride remained the only risk factor to be significantly improved.

Comparing mean changes from baseline, there was no difference in weight loss between the 2 diets at 3 or 6 months, when analyzing completers as well as intent to treat.

A subgroup of 46 postmenopausal women lost significantly more weight on the low carbohydrate diet than the high carbohydrate diet (P < 0.05).

Author Conclusion:
A 1200 kcal diet composition of 58% energy from carbohydrate was palatable.  It did not lead to greater weight loss or risk facotr improvement than a 1200 kcal diet of 35% energy from carbohydrate in this 6 month study of 110 free living women, however, it did result in a significant improvement in blood lipids at 3 and 6 months, giving some reasons for preferring high carbohydrate diets in routine use.  Dropouts on the 2 diets were similar at about 25% over 6 months.
Funding Source:
Government: National Research Council (UK)
Industry:
Diet & Health Food Company Limited (UK)
Food Company:
University/Hospital: University of Glasgow (UK)
Reviewer Comments:
Large sample size.  Actual intake not reported, compliance not monitored.  Recruitment not defined.
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? ???
  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? Yes
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) No
  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? 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? ???
  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? ???
  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)? 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? 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