DF: Cardiovascular Disease (2008)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
The purpose of this 24-week study was to investigate the effect of fiber supplements on body weight and blood lipids in healthy overweight females.
Inclusion Criteria:
  • Age: 18 to 67 years
  • BMI: Over 27.5kg/m2.
Exclusion Criteria:
  • Serious cardiac, renal and hepatic disease
  • History of gastrointestinal disease, type 1 diabetes, pregnancy
  • Patients treated with antacids, diuretics, H2-blockers, bulk laxatives, anorectics and oral contraceptives.
Description of Study Protocol:
  • Recruitment: Participants were recruited through announcements in the local newspaper
  • Design: Randomized, placebo-controlled study. Patients were randomized based on BMI, but the specific randomization procedures are not described. 
  • Blinding used: Double-blind.

Intervention

  • Fiber: The intervention group was prescribed fiber tablets (Farma Food, Copenhagen, Denmark) and the placebo group was prescribed placebo tablets (identical in taste in appearance to the fiber tablets)
    • For the first eight weeks (high dose), the tablets were taken four times daily including six tablets taken 15 minutes before meals with 250ml of water and four tablets taken at 3:00 pm
    • For the remaining 16 weeks (maintenance dose), the tables were reduced to five tablets three times daily
    • The high dose fiber period provided approximately six grams of fiber and the maintenance dose provided four grams of fiber
    • The fiber tablets were a mixture of fibers from grain and citrus and consisted of 15% soluble fiber and 85% insoluble fiber.
  • Diet and lifestyle: Patients were told to follow a 1,200-kcal diet (with an estimated 15g of fiber per day), perform their regular exercise program and not change their smoking habits during the study
  • Multivitamin: All subjects received a multi-vitamin equal to 100% of the RDAs for vitamins and minerals
  • Motivational session: During three group sessions throughout the treatment period, subjects were informed of the health consequences of overweight in attempt to keep them motivated.

Statistical Analysis

  • Analysis was performed in patients who fulfilled the study protocol 
  • Wilcoxon rank sum tests
  • Paired Student’s T-tests.
Data Collection Summary:

Timing of Measurements

  • Physical exams to assess the dependent variables were conducted at baseline and weekly for the first 12 weeks and every fourth week during the remaining treatment period.
    • Weight (procedures not specified)
    • Systolic and diastolic blood pressure (procedures not specified)
    • Fasting blood sample which included hemoglobin, glucose, cholesterol, triglycerides, uric acid, sodium and potassium.
  • Tablet compliance assessed by returned tablets; 80% compliance was considered acceptable.
    • Fiber tablets: 22 tablets or six grams of fiber for the first eight weeks (high dose) and then 15 tablets or four grams of fiber during the remaining 16 weeks (maintenance dose)
    • Placebo tablets: 22 placebo tablets during the first eight weeks and 15 placebo tablets during the remaining 16 weeks. 
  • 1,200-kcal diet: Evaluated regularly using a standardized questionnaire (procedures not specified). Dietary adherence of 20% was considered acceptable.
  •  Motivational session: Offered three times during the treatment period (no details provided).

Dependent Variables

  • Weight
  • Systolic and diastolic blood pressure
  • Chemistries: Hemoglobin, glucose, cholesterol, triglycerides, uric acid, sodium and potassium.

Independent Variables

Fiber supplement.

Control Variables

None.

Description of Actual Data Sample:
  • Initial N: 60 women (30 in each group) were randomized to the fiber or placebo treatment group. Seven of these subjects did not enter the study due to sudden events between randomization and start of the study.
  • Attrition (final N): 53 subjects (28 in the fiber group and 25 in the placebo group) entered the study and completed the study according the protocol
  • Age: Fiber group (N=28), 37.0±1.7 years; placebo group (N=25), 43.2±2.1 years
  • Ethnicity: Not provided
  • Anthropometrics: There were no significant differences between groups for age, body weight, BMI and duration of overweight
  • Location: Norway.
Summary of Results:

Weight

There was a significant weight loss (P<0.05) in the fiber group from Week Four and onwards, as compared to the placebo group. After the 24-week treatment, mean weight loss in the fiber group was 8.0kg vs. 5.8kg in the placebo group (P<0.05).

Blood Pressure and Biochemical Parameters at Baseline and After Treatment

Variables

Fiber Group at Baseline
(Means±SEM)

Fiber Group at 24 Weeks
(Means±SEM)

Placebo Group at Baseline
(Means±SEM)

Placebo Group at 24 Weeks
(Means±SEM)

Systolic Blood Pressure

127.5±2.7

120.5±2.6*

134.0±3.1

126.8±2.1*

Diastolic Blood Pressure

81.1±2.3

70.5±1.6*

82.9±2.2

74.6±1.5*

Hemoglobin

13.5±0.1

12.6±0.2*

13.9±0.1

13.1±0.2*

Glucose

5.3±0.1

5.1±0.1*

5.6±0.1

5.2±0.1*

Cholesterol

5.7±0.2

5.2±0.2*

6.0±0.3

5.5±0.2*

Triglycerides

1.34±0.2

0.92±0.1*

1.47±0.2

0.92±0.1*

Uric Acid

270±11

217±10*

259±14

206±12*

* Significant difference from baseline value. 

There were no significant between-group differences for systolic and diastolic blood pressure, hemoglobin, cholesterol, triglycerides and uric acid. (Between-group differences for glucose is not discussed).

Other Findings

Treatement did not change serum concentrations of potassium and sodium.

Author Conclusion:
  • A high patient compliance and sustained weight reduction was achieved using a treatment regimen with a combination of a hypocaloric diet and a dietary fiber supplement, in addition to regular information meetings
  • Weight loss was more profound in the supplemental fiber group than in the placebo group
  • This study did not confirm that a dietary fiber supplement can enhance a reduction of cholesterol and triglycerides beyond that of a hypocaloric diet. 
Funding Source:
University/Hospital: Unversity Hospital of Tomso, Karolinska Hospital (both Sweden)
Reviewer Comments:
  • The biggest limitation of this study is the lack of detail regarding dietary assessment
  • Data related to dietary intake are not presented; it is unclear if total caloric or dietary fiber intake between the groups were similar throughout the duration of the study
  • Lack of this critical detail clouds interpretation of the results. The reference to the 1,200-kcal diet states that "an adherence rate of 20% was considered acceptable." This is problematic, as 20% adherence is extremely low. Details regarding dietary intake needs further clarification with supporting data.
  • Otherwise, the remaining criteria areas recieve favorable ratings.
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) 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? 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? No
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? No
  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? ???
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? No
  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? No
  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? No
  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? No
  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? No
  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? No
  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? No
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