DF: Obesity (2008)
Citation:
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
To evaluate the effectiveness of an agar diet in weight management in individuals with type 2 diabetes and impaired glucose tolerance.
Inclusion Criteria:
- Outpatients in the HEC Science Clinic
- Presence of type 2 diabetes without medications
- Presence of impaired glucose tolerance without medications
- HbA1C under 8.0
- BMI over 25.
Exclusion Criteria:
Microvascular or macrovascular complications of diabetes.
Description of Study Protocol:
- Recruitment: Outpatients undergoing diet and exercise therapy in the HEC Science Clinic with type 2 diabetes or impaired glucose tolerance
- Design: Randomized.
Intervention
- Run-in period four weeks
- Randomization
- 12 weeks of a conventional diet (nine with impaired glucose tolerance, 29 with type 2 diabetes)
- 12 weeks of an agar diet (eight with impaired glucose tolerance, 30 with type 2 diabetes).
- Energy intake was 400kcal less than energy output
- Agar diet
- 25% fat, 60% carbohydrates, 15% protein, maximum of 300mg cholesterol
- 180 grams of agar 15 minutes before the meal (30kcal, 4.5g of fiber).
- 30 minutes of moderate-intensity exercise at least three days per week
- Subjects kept food records that were reviewed by a dietitian
- Both groups received nutrition guidance every one or two months while in the experimental component
- Chemistries taken following overnight fast every four weeks.
Statistical Analysis
- Mean±SD
- Unpaired T-tests
- Analysis of variance (ANOVA)
- Statistical significance at P<0.05
- SPSS version 10.0 for Windows.
Data Collection Summary:
Timing of Measurements
- Fasting blood samples every four weeks: Plasma glucose, total cholesterol, HDL, triacylglycerol and HbA1C
- Oral glucose tolerance test (75g) obtained before and after the 12-week experimental period: Blood samples for glucose tolerance test were taken at 0, 30-, 60-, 90- and 120-minute intervals.
Dependent Variables
- Plasma glucose measured by glucose oxidase method
- Insulin measured by double antibody-radioimmunoassay
- Total cholesterol, HDL and triacylglycerol measured with enzymatic processes
- HbA1C measured by high-performance liquid chromatography
- Homeostasis model assessment used to measure insulin resistance, fasting insulin, glucose area under the curve and insulin area under the curve
- DEXA measurement for total body fat
- CT scan for visceral fat and subcutaneous fat.
Independent Variables
- Agar diet (25% fat, 60% carbohydrates, 15% protein, maximum of 300mg cholesterol)
- 180 grams of agar consumed before each meal.
Control Variables
Conventional (or usual) diet.
Description of Actual Data Sample:
- Initial N: 76 (28 males, 48 females)
- Attrition (final N): Not described
- Age: 58.6±6.4 years
- Ethnicity: Not described
- Anthropometrics: No significant differences between groups in baseline characteristics
- Location: HEC Science Clinic, Isogo-ku, Yokohama-shi, Kanagawa, Japan.
Summary of Results:
- No significant differences between the diet groups related to clinical backgrounds
- Body weight decreased in both diet groups (4.4% weight reduction in the agar diet group and 2% weight reduction in the control group)
- Fasting plasma glucose decreased in both groups, but was significant only in the agar diet group (P<0.001)
- Systolic and diastolic measurments decreased significantly in both groups
- Total cholesterol decreased significantly only in agar diet group (P<0.05)
- HDL increased in both groups, with no significant differences
- Triacylglycerol decreased in both groups, with no significant differences
- Fasting insulin decreased significantly only in the conventional diet group (P<0.01)
- Insulin resistance decreased significantly in both groups (P<0.01)
- Although insulin area under the curve and glucose area under the curve decreased in both groups, there were no signicant differences
- The agar diet group had significant decreases in total body fat (P<0.001), visceral fat (P<0.05) and subcutaneous fat (P<0.01)
- Improvement in terms of body weight (-2.8±2.7kg vs. -1.3±2.3kg, P=0.008), BMI (-1.1±1.1kg/m2 vs. - 0.5±0.9kg/m2, P=0.009) and total cholesterol (-7.6±27.5mg per dL vs. +2.4±23.4mg per dL, P=0.036) were significantly greater in the agar-diet group.
Author Conclusion:
The agar diet had a significant positive effect on HbA1C, total cholesterol, total body fat, visceral fat and subcutaneous fat.
Funding Source:
University/Hospital: | HEC Scientific Client, Yokohama City University |
Reviewer Comments:
- No description of dietary fiber intake
- No discussion of compliance
- Energy output measured by calorie counter.
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? | No | |
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? | 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%.) | No | |
4.3. | Were all enrolled subjects/patients (in the original sample) accounted for? | Yes | |
4.4. | Were reasons for withdrawals similar across groups? | N/A | |
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.) | 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? | 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? | No | |
6.5. | Were co-interventions (e.g., ancillary treatments, other therapies) described? | No | |
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)? | N/A | |
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? | N/A | |
9. | Are conclusions supported by results with biases and limitations taken into consideration? | No | |
9.1. | Is there a discussion of findings? | Yes | |
9.2. | Are biases and study limitations identified and discussed? | No | |
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 | |