EAL

DF: Cardiovascular Disease (2008)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To investigate whether a fiber supplement aids in promoting and maintaining weight loss.

Inclusion Criteria:

Females
Ages 18 to 55 years old
Body weight between 110% and 130% ideal body weight (Metropolitan LIfe Tables)
Gave informed consent.

Exclusion Criteria:

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.

Description of Study Protocol:

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.

Data Collection Summary:

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.

Description of Actual Data Sample:

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.

Summary of Results:

Variables	Fiber Group, N=62 (Mean±SEM)	Placebo Group, N=35 (Mean±SEM)	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.

Author Conclusion:

Adding a supplement of dietary fiber to a hypocaloric diet promotes higher weight loss as well as weight maintenance.

Funding Source:

University/Hospital:

University of Olso

Reviewer Comments:

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
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