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MNT: Weight Management (2015)

Citation:

Bahadori B, Yazdani-Biuki B, Krippl P, Brath H, Uitz E and Wascher TC. Low-far, high-carbohydrate (low glycaemic index) diet induced weight loss and preserves lean body mass in obese health subjects: Results of 24 week study. Diabetes, Obesity and Metabolism. 2005; 7: 290-293.

PubMed ID: 15811147
 
Study Design:
Before-After Study
Class:
D - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:
To investigate the long-term effect of a low-fat diet with unrestricted low glycemic index (GI) carbohydrates in obese, non-diabetic patients.
Inclusion Criteria:
  • Aged 18 years to 65 years
  • Body mass index (BMI) 26kg/m2 to 49 kg/m2
  • Willing to lose weight
  • Passed medical examination
  • Informed consent provided.
Exclusion Criteria:
  • Use of any prescription medications
  • Pregnant or breastfeeding
  • Following any weight loss diet during the past three months.
Description of Study Protocol:

Recruitment

Recruited from two obesity outpatient clinics.

Design

Obese patients were recruited from two obesity clinics. Subjects were given advice on the low gylcemic index diet by a dietitian and then attended biweekly one-hour group meetings that induced dietary and supportive counseling. Body weight and body composition were measured at baseline and after 24 weeks.

Intervention

Low-fat, low glycemic index diet through education and recommendations provided by dietitian.

Statistical Analysis

  • Wilcoxon signed rank test
  • P<0.05 are significant.
Data Collection Summary:

Timing of Measurements

  • Weight and body composition (fat mass and lean body mass) were measured at baseline and after 24 weeks
  • Food diaries were completed by subjects during the last seven days of the dietary period.

Dependent Variables

  • Weight 
  • BMI
  • Fat mass
  • Lean body mass.

Independent Variables

Education on low-fat, low-GI diet was provided by a dietitian.

Control Variables

Compliance with low-fat, low-GI diet.

 

Description of Actual Data Sample:
  • Initial N: N=120 subjects (66 females and 54 males)
  • Attrition (final N): N=109 subjects (61 females and 48 males)
  • Age: Mean age 44 years
  • Anthropometrics: Differences in baseline anthropometrics not evaluated
  • Location: Austria.
Summary of Results:

Key Findings

  • After 24 weeks, average weight loss was 8.9kg (98.6kg vs. 89.7kg; P≤0.0001)
  • Significant loss in fat mass (42.5kg vs. 36.4kg; P≤0.0001) and a decrease in lean body mass of 5.0% (56.1kg vs. 53.3kg; P≤0.0001) after 24 weeks
  • Significant decrease in BMI (P≤0.0001) after 24 weeks.
 
Variables Males Females
  Week Zero Week 24 P-value Week Zero Week 24 P-value
Weight (kg) 108.9±24 98.8±23.7 ≤0.0001 90.4±13 82.5±11.4 ≤0.0001
BMI (kg/m2) 34.2±4.7 31±4.8 ≤0.0001 32.7±4.0 29.8±3.5 ≤0.0001
Fat mass (kg) 47.9±11.2 41.1±11 ≤0.0001 38.2±8.5 32.7±7.1 ≤0.0001
Lean body mass (kg) 61.1±15.1 57.7±15.3 ≤0.0001 52.2±7.5 49.8±7.0 ≤0.0001
 

Data expressed as mean ±SD.

Other Findings

Adherence to diet:
  • Category one (adhered exactly to advice given): 60% of subjects
  • Category two (did not completely adhere to advice given but dietary intake was acceptable): 31% of subjects
  • Category three (did not adhere to advice given and dietary intake was unacceptable): 9% of subjects.
Author Conclusion:
The six-month uncontrolled study using a low-fat, low-GI diet led to a significant reduction in body mass and fat mass with a considerable smaller reduction in lean body mass. Good adherence to the diet and a low dropout rate were observed.
Funding Source:
Other: Not described
Reviewer Comments:
  • Study did not have control group
  • Attendance at group meetings was not described. 
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? 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? 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? N/A
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? Yes
  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? No
  6.6. Were extra or unplanned treatments described? No
  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)? No
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? No
  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? No
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? No
  10.2. Was the study free from apparent conflict of interest? Yes