DF: Obesity (2008)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:

To evaluate the effets of dietary fiber administration before meals on hunger ratings in obese subjects.

Inclusion Criteria:
  • Current participation in the "Slim Club" weight-loss program, a weekly group that meets for instruction about food preparation, nutrition education and general support
  • Formal calorie counting is not a part of the program, but recipes are provided for guidance
  • Physical activity is not a formal part of the program, but is strongly encouraged. 
Exclusion Criteria:

None specified.

Description of Study Protocol:
  • Recruitment: Both treatment and control groups were recruited from members of the Slim Club weight-loss program in Stockholm, Sweden.
  • Design: Randomized controlled trial.
  • Blinding used: None specified. 

Intervention

Subjects divided into three groups:

  • Those receiving 6.6g of bran fiber 15 minutess before meals (with half a glass of water)
  • Those receiving 6.6g ispaghula fiber before meals
  • Those receiving no fiber before meals (control).

Statistical Analysis

  • Three groups were compared by the Kruskal Wallis test
  • Wilcoxon's rank sum test was used for paired comparison. 

 

Data Collection Summary:

Timing of Measurements

  • Hunger measurements were recorded before each meal (breakfast, lunch, dinner) and also at 3:00 pm
  • The intervention lasted for three weeks (with the first week being a "run-in," in which no fiber was given; subjects only recorded data regarding their hunger state).

Dependent Variables

  • Hunger Ratings: Subjectively evaluated on a visual analogue scale, by a mark across a 100-mm horizontal line, with extremes marked "not at all hungry" and "very, very hungry"
  • Weight.

Independent Variables

Use of fiber (either bran, ispaghula or none). 

Control Variables

N/A.

Description of Actual Data Sample:
  • Initial N: 135 subjects (eight male); 50 in each treatment group; 35 in control
  • Attrition (final N): 110 subjects (43 ispaghula, 44 bran, 23 control)
  • Mean age: 42 years (range, 15 to 72)
  • Ethnicity: Not specified
  • Other relevant demographics: Not specified
  • Anthropometrics: No significant differences in weight at baseline
  • Location: Stockholm, Sweden.
Summary of Results:
Group N Height (cm) Initial Weight (kg) Final Weight (kg)
Ispaghula 43 168±7 80.4±17.3 76.2±16.3
Bran 44 166±6 75.1±13.0 70.5±12.1
Control 23 164±6 76.9±9.4 72.3±9.5
*Significantly different than baseline, P<0.05.
  • Hunger ratings were significantly lower, compared to controls in the Ispaghula (P<0.01) and Bran Groups (P<0.05), at both breakfast and dinner
  • For all groups, hunger rating at breakfast was low and increased during the day to peak immediately before dinner
  • After one week of fiber treatment, a significant reduction of hunger ratings was observed in both fiber groups
    • Hunger ratings were lower both before meals and at the 3:00 pm rating between meals 
    • Hunger rating reduction observed after one week of fiber addition was sustained during the last week of the study, when essentially the same hunger reduction pattern was observed 
    • No significant differences between fiber treatment groups were reported 
    • No specific numbers were provided for hunger rating scores, only a graph [Figure 2 in text].
Author Conclusion:

The addition of dietary fiber immediately before meals reduced hunger feelings, but had no effect on weight reduction among members of the Slim Club weight loss group. 

Funding Source:
University/Hospital: Karolinska, King Gustaf V Medical Center
Reviewer Comments:
  • The large attrition rate in the Control Group (12 subjects lost, out of 35), compared to the withdrawal rate of the treatment (six and seven out of 50 from both the bran and ispaghula groups respectively), is a potential cause for concern 
  • There was no discussion as to why a placebo was not included in the study design 
  • The numbers in the abstract regarding sample size are different from those quoted in the text, so it can't truly be said that all subjects are accounted for 
  • Not certain if a two-week treatment with fiber is enough to determine whether a particular intervention can have a signfiicant impact on weight loss or that providing fiber 15 minutes before meals is the optimum time for dosing 
  • No randomization method was identified in the paper.
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? No
  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? No
  2.2. Were criteria applied equally to all study groups? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? No
  2.4. Were the subjects/patients a representative sample of the relevant population? No
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? No
  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? ???
  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? 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? 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? ???
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? No
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? Yes
  6.6. Were extra or unplanned treatments described? N/A
  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? ???
  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? 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? No
  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