DM: Fiber (2014)

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

1. To see if the improved knowledge, compliance and metabolic control shown in a previous study maintained after stopping formal education

2. To determine if patients obtain further benefit by changing to a diet containing less fat and more high fiber carbohydrate

3. To determine how well patients and their families respond to the high fiber/low fat diet.

Inclusion Criteria:
Type 1 diabetes, poor metabolic control
Exclusion Criteria:
None provided (may have been in an earlier published article: Br Med J. 1983; 2:1858-1861).
Description of Study Protocol:


All subjects from a previous study were asked if they would be willing to continue for a further 10 months


Comparison of metabolic control in 12 subjects with type 1 diabetes randomized to follow a high carbohdyrate/high fiber/low fat diet for 10 months vs 10 subjects following "previous diet education" (conventional low carbohydrate diet with previous lunchtime demonstration/videotape education) for 6 months, and another 12 subjects in a control group (conventional low carbohydrate diet with previous dietitian instruction only) for 6 months.

Blinding used (if applicable) no

Intervention (if applicable)

Subjects in the intervention group were asked to increase their carbohydrate daily intake to be approximately 50% of energy through use of fiber-rich unprocessed foods and bean and lentils, and to eat vegetables and fruit liberally at both midday and evening meals.  Subjects were seen in small groups (with spouses where possible) and received printed instructions and recipe books, with dietitian/educational followup at 1, 2, and 4 months after initial instructions. No new dietary advice or teaching was given during the final 6 months unless specifically requested.  The control group and the previous diet group continued their usual diets for 6 months. 

Statistical Analysis

  • Paired non-parametric statistical tests:
  • Wilcoxon matched sign rank test to measure progressive changes within each group
  • Mann-Whitney method for testing comparisons between groups


Data Collection Summary:

Timing of Measurements

  • Control groups: End of first educational intervention, 6 months
  • Intervention group: End of first educational intervention, 4 months (end of second educational intervention), 10 months

NOTE: End of first educational intervention period refers to first part of this study (McCulloch, Br Med J 1983, 1858-61)

Dependent Variables

  • Dietary knowledge (questionnaire - knowledge of 10g carbohydrate exchanges)
  • Dietary compliance (7-day food records for carbohydrate: 6 coefficients of variation were derived from each food record, one for each meal and snack; an average was calculated, providing a measure of day-to-day consistency in carbohydrate intake)
  • HbA1 (electrophoretic method on cellulose acetate membranes - Clin Chem, 1983)

Control Variables

  • Fiber, calories, and macronutrient percentages of calories (7-day food records, averaged)

Independent Variables

  • BMI
  • Insulin dose
Description of Actual Data Sample:

Initial N: 37

Attrition (final N): 34 (19 men, 15 women)

Age: (see table below)

Ethnicity: not provided

Other relevant demographics:


Intervention Group n=12


Previous Diet Ed  Control Group n=10


Control Group n=12


Statistical difference between groups 
Age (yrs) 39.3±3.9 29.8±2.8 38.1±2.6 NS
Duration of diabetes (yrs) 14.3±1.8 11.6±1.3 11.5±1.8 NS
Insulin dose ( 0.67±0.03 0.88±0.08 0.67±0.07 NS
BMI (kg/m2) 24.3±0.5 23.2±0.8 24.4±0.8 NS

Anthropometrics: (see above table)

Location: University Hosdpital, Queens Medical Centre, Nottingham, UK


Summary of Results:


Measures Intervention Group n=12 Previous Diet Ed Control Group n=10

Control Group n=12

Statistical difference between groups 

HbA1(%) end of 1st intervention period (see note)

9.4±0.5* 10.3±0.7** 12.0

*p<0.002 compared to control

**p<0.05 compared to control

HbA1(%) end of 2nd intervention period 11.2±0.5 ------- ------- p<0.01 compared to end of 1st intervention period
HbA1(%) six mo after intervention 10.0±0.6* 9.5±0.4**  12.5±0.3

 *p<0.02 compared to control

**p<0.002 compared to control

Fiber (g) intake, six mo after intervention(s) (see note) 31.8±1.7* 28.5±3.0** 20

*p< 0.02 compared to control

**P<0.05 compared to control; NS from intervention group


Note: groups were not statistically different in HbA1c at beginning of initial study

Note: fiber intake at beginning of initial study was ~20 g/day for all groups

Other Findings

  • Daily insulin dose and BMI did not change significantly within or between groups throughout the study.
  • There was no significant change in calorie intake either within or between groups throughout the study.
  • Intervention group significantly reduced fat (43% of calories as fat to 34%) and increased carbohydrate (38% of calories as carbohydates to 45%) whereas the control groups had no significant change in these macronutrients throughout the study
  • Intervention group and previous diet control group were significantly more consistent in carbohydrate from day-to-day at the end of the study than the control group, and showed significant improvement in knowledge compared to the control group
  • None of subjects in intervention group changed their eating habits or those of their families nearly as much as was recommended.
Author Conclusion:
Imaginative and practical teaching methods are the most important factor influencing dietary compliance and metabolic control in type 1 diabetic adults, and no additional improvement is achieved in this group by changing to a high carbohydrate/high fiber/low fat diet.
Funding Source:
University/Hospital: Britsh Diabetic Association
Reviewer Comments:
  • small number of subjects
  • method for determining fiber in diet not described  (e.g.:from a database?)
  • This study (without modern insulin management and completed during a period of time where "diabetic diets were just beginning to trend to higher carb, lower fat) is a "real world" one where subjects are provided innovative education designed to change "diet", and then left on their own for six  months to see what happens (vs a closely controlled clinical study, for example in a GCRC, or for outpatients that are closely followed).
  • Because this study is an extention of a study previously published, it is difficult to "tease out" the relevant information for just the intervention presented
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? ???
  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? ???
  2.2. Were criteria applied equally to all study groups? ???
  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? No
3. Were study groups comparable? ???
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) ???
  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? No
  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? N/A
  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? N/A
  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? 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)? N/A
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? ???
  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? 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