DF: Cardiovascular Disease (2008)
To investigate whether a fiber supplement aids in promoting and maintaining weight loss.
- Females
- Ages 18 to 55 years old
- Body weight between 110% and 130% ideal body weight (Metropolitan LIfe Tables)
- Gave informed consent.
- Males
- Age under 18 years or 56 years and older
- Known gastrointestinal disease
- Use of certain medications: Diuretics, bulk laxatives, H2 blockers, appetite-suppressing agents, neuroleptics or anti-depressive drugs
- Subjects who had started estrogen therapy within the preceding six months.
Recruitment
Members of Libra Slimming Club from six different regions of Norway were invited to participate.
Design
- Randomized double-blind, placebo-controlled trial for 52 weeks
- Randomization scheme not described.
Blinding Used
Subjects and investigators were blinded to fiber supplement or placebo.
Intervention
- Part I (first 11 weeks): All subjects received a 1,200-kcal diet and either a fiber supplement (total seven grams daily) or a placebo to be taken with 200ml of water 15 minutes before meals. Subjects had a weekly check-up.
- Part II (second 16 weeks): 1,600-kcal diet and either a fiber supplement (total, six grams daily) or a placebo to be taken with 200ml water 15 minutes before meals. Subjects had a bi-weekly check-up.
- Part III (final 25 weeks): Ad libitum diet with all participants receiving a fiber supplement (total, six grams daily) to be taken with 200ml water 15 minutes before meals. Subjects had a monthly check-up.
- The fiber supplement was primarily insoluble fiber (10:1 insoluble to soluble fiber, respectively).
Statistical Analysis
- Results were given as mean and standard error of the mean (one-tailed tests used)
- Differences significant if P≤0.05
- Wilcoxon signed midrank test to evaluate differences within group
- Wilcoxon midrank-sum test used for comparisons between groups
- Intent-to-treat analyses with dropout and withdrawal given last and highest observed values, respectively
- Kaplan-Meier method used to estimate probability of adherence to treatment
- Gehan's test with Aalen's modification used to compare groups.
Timing of Measurements
- Adherence to fiber supplement or placebo (pills counted at each visit)
- Bowel movements (evaluated three times during Part I and at each check-up visit)
- Weight (baseline and at each check-up visit).
Dependent Variables
- Body mass index: Kg per m2
- Waist-to-hip ratio: Waist measured in cm; hip measured in cm
- Adherence to treatment: Counted fiber supplement or placebo pills returned at check-up visits
- Blood pressure: Measured change in systolic and diastolic pressures
- Feelings of hunger: Measured by visual analog scale with descriptive anchors at each end for four meals (breakfast, lunch, afternoon snack, dinner)
- Heart rates: Beats per minute.
Independent Variables
Fiber supplement or placebo.
Control Variables
- Energy value of diet
- Part I (Weeks One to 11): 1,200kcal
- Part II (Weeks 12 to 27): 1,600kcal
- Part III (Weeks 27 to 52): Ad libitum.
- Initial N: 107 (zero males, 107 females)
- Attrition (final N): 97.
Age
NS difference between groups (P>0.5)
- Fiber group: Mean age, 39.6±1.9 years
- Placebo group: Mean age, 36.6±2 years.
Ethnicity
Norwegian.
Other Relevant Demographics
Not described.
Anthropometrics
Mean BMI: 27.4±3 (both treatment and placebo groups).
Location
Norway.
Variables |
Fiber Group, N=62 |
Placebo Group, N=35 |
Statistical Significance of Group Difference |
Weight Change After 11 Weeks |
-4.9kg |
-3.3 kg |
P<0.05 |
Weight Change After 27 Weeks* |
-3.8±0.5kg |
2.8±0.9 kg |
P<0.05 |
Total Weight Change After 52 Weeks |
-6.7kg |
N/A** |
N/A** |
Change in BMI |
-1.4±0.2kg/m2 |
-0.9±0.3kg/m2 |
P=0.03 |
Change in Waist-to-Hip Ratio After 27 Weeks |
-0.02±0.01 |
-0.01±0.01 |
P=0.3 (NS) |
Change in Diastolic BP |
-3.7mmHg |
No change |
P<0.05 |
Number of Bowel Movements Per Week |
7.4±0.8 |
6.3±0.6 |
P>0.05 (NS) |
*Both groups regained some weight between Weeks 11 and 27
**Not applicable, as placebo was discontinued and all subjects received fiber supplement after 27 weeks
Other Findings
- Probability of adherence to treatment was significantly higher in the fiber group after 13 weeks of treatment and persisted throughout the trial (P<0.01)
- Feelings of hunger at lunch, 3:00 pm and at dinner time decreased in the fiber group and increased in placebo group. Hunger feeling were significantly lower (P<0.04) in the fiber group at those three meals compared to placebo. No difference in feelings of hunger at breakfast.
Adding a supplement of dietary fiber to a hypocaloric diet promotes higher weight loss as well as weight maintenance.
University/Hospital: | University of Olso |
- No discussion of attrition in Parts II and III
- Dietary fiber not quantified for Part III
- Results from Weeks 27 to 52 may have been confounded by combining groups and giving all subjects the fiber supplement.
Quality Criteria Checklist: Primary Research
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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%.) | No | |
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? | 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? | 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? | 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)? | No | |
8.6. | Was clinical significance as well as statistical significance reported? | No | |
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 | |