DM: Prevention and Treatment of CVD (2007)
proteinuria
Recruitment
Public advertisement
Design
Comparison, by diet (high protein vs lower protein), of insulin sensitivity and body composition at 0 and 8 weeks (weight loss period) and after a further 4 weeks (weight stable period) in individuals with type 2 diabetes
Blinding used (if applicable)
None described
Intervention (if applicable)
- High protein diet: 30% energy from protein, 40% from carbohydrate, and matched for fatty acid profile (8% saturated, 12% mono, 5% poly)
- Lower protein diet: 15% energy from protein, 60% from carbohydrate, and matched for fatty acid profile (8% saturated, 12% mono, 5% poly)
- First eight weeks (weight loss period) kcal were restricted to 1600; during the last 4 weeks, caloric intake was increased by 30%, and protein was increased by 7 g in the LP diet and 21 g in the HP diet.
- Foods were eaten on an outpatient basis, with fixed menu plans, and with subjects receiving preweighed key foods (about 60% of energy intake)
- Meeting every two weeks with research dietitian for dietary instructions/assessment
Statistical Analysis
- repeated measures ANOVA
- one-way ANOVA (baseline differences between diets and men and women)
- no power calculations
Timing of Measurements
Baseline (0), 8, and 12 weeks
Dependent Variables
- Fat amount and distribution: dual-energy X-ray absorptiometry (DEXA), wks 0 and 12
- Insulin sensitivity: continuous low-dose glucose (SSPG) and insulin (SSPI) infusion test (3 hr) for steady-state plasma glucose and insulin (refinement of a modified Harano test), weeks 0 and 12
- Fasting plasma glucose: enzymatic kit/Cobas-Bio analyzer
- Fasting serum total cholesterol: enzymatic kit/Cobas-Bio analyzer
- Fasting serum triacylglycerol: enzymatic kit/Cobas-Bio analyzer
- Fasting plasma HDL cholesterol: precipitation of LDL and VLDL/Cobas-Bio analyzer
- LDL cholesterol: calculated with a modified Friedewald equation
- Fasting insulin: radioimmunoassay kit (Pharmacia & Upjohn Diagnostics)
- HbA1c: high-performance liquid chromatography
Independent Variables
- High protein diet: 30% energy from protein, 40% from carbohydrate, and matched for fatty acid profile (8% saturated, 12% mono, 5% poly)
- Lower protein diet: 15% energy from protein, 60% from carbohydrate, and matched for fatty acid profile (8% saturated, 12% mono, 5% poly)
- First eight weeks (weight loss period) kcal were restricted to 1600; during the last 4 weeks, caloric intake was increased by 30%, and protein was increased by 7 g in the LP diet and 21 g in the HP diet.
- Foods were eaten on an outpatient basis, with fixed menu plans, and with subjects receiving preweighed key foods (about 60% of energy intake)
- Meeting every two weeks with research dietitian for dietary instructions/assessment
- Food records, 3 consecutive days (2 weekdays, 1 weekend day) every 2 weeks: Diet/1 Nutrition Calculation software, (Xyris Software, 1998)
- physical activity: 24-hr activity recall
- alcohol (subjects asked not do drink during the study
Control Variables
- type 2 diabetes
- age
- gender
- Urine urea and creatinine from 24-h urine collections: Hitachi autoanalyzer (Roche)
- medications
- blood pressure
Initial N: 66
Attrition (final N): 54 (19 men, 35 women). 18% dropout rate. 2 subjects withdrew before commencement. 10 subjects (5 from each diet group) withdrew throughout the study.
Age: men, 64 yrs; women, 60 y. 26 on HP diet, 28 on LP diet.
Ethnicity: not provided
Other relevant demographics: none provided
Anthropometrics: Authors indicate no significant differences between variables (age, BMI, weight, glucose, insulin, SBP, DBP) by diet for men or women at baseline
Location: CSIRO Health Sciences and Nutrition, Adelaide, Australia
HP Diet LP Diet
Variables* |
0 wk mean±SEM |
8 wk mean±SEM |
12wk mean±SEM |
0 wk mean±SEM |
8 wk mean±SEM |
12 wk mean±SEM |
Difference between diets |
Weight (kg) |
97.7±17.4 | 93.2±16.7 | 92.2±16.8 | 91.4±18.2 | 86.9±16.9 |
86.6±16.8 |
NS |
Fat mass (men) |
38.7±5.0 | 35.5±2.6 | 34.8±5.2 |
|
30.4±2.4 |
NS |
|
Fat mass (women) | 42.8±2.6 | 37.5±2.5 | 39.9±3.2 |
|
37.0±3.1 |
p<0.05 |
|
Fasting glucose | 8.44±0.41 | 7.30±0.28 | 7.70±0.31 | 7.76±0.24 | 7.02±0.21 | 7.33±0.30 | NS |
Fasting insulin | 16.3±7.2 | 12.1±6.5 | 13.3±6.8 | 16.5±7.7 | 14.0±10.8 | 14.8±9.2 | NS |
HbA1c | 6.42±0.83 | 5.88±0.78 | 6.30±0.77 | 5.79±0.59 | NS | ||
Total cholesterol | 5.16±0.17 | 4.64±0.18 | 4.81±0.16 | 5.16±0.25 | 4.82±0.22 | 5.15±0.25 | p<0.01 |
Triglyceride | 2.02±0.15 | 1.56±0.13 | 1.68±0.14 | 2.17±0.21 | 1.76±0.11 | 1.94±0.16 | NS |
LDL chol | 3.32±0.16 | 3.02±0.15 | 3.13±0.15 | 3.23±0.20 | 3.12±0.20 | 3.32±0.22 | p<0.05 |
HDL chol | 0.93±0.03 | 0.92±0.03 | 0.92±0.04 | 0.95±0.05 | 0.91±0.04 | 0.96±0.03 | NS |
*while units were not provided, fat mass is probably kg; fasting insulin is mU/L, HbA1c is %, and fasting glucose and lipids are all mmol/L
Other Findings
- Dietary fiber was significantly lower and dietary cholesterol, significantly higher on the high protein diet compared to the lower protein diet
- Urinary urea/creatinine ratio was significantly different between diets, indicating good dietary compliance. Dietary records also indicated good compliance (HP = 28% protein, 42% carbohydrate, 28% fat; LP = 16% protein, 55% carbohydrate, 26% fat)
- There was a significant sex by diet interaction for
- total fat mass (women lost more on the HP diet whereas men lost more on the LP diet, p=0.01
- abdominal fat mass (women lost more on the HP diet whereas men lost more on the LP diet, p<0.02
- Total lean mass was reduced significantly (2.1%) with both diets, NS between diets
- SSPG concentrations decreased significantly from baseline to week 12 (12.1 to 10.7 mmol/l, p= 0.01), NS between diets; the same was true for SSPI (523 to 428 pmol/l, p=0.003) with no effect of diet or sex
- SBP fell significantly by 8 mmHg and DBP by 4 mmHg at week 8 (p<0.01), NS between diets. During weight stabilization period, SBP rose by 3 mmHg and DBP by 1 mmHg (p<0.001)
- Decreases in glucose lowering medications occurred in 5 subjects from the HP diet group and 3 from the LP group; antihypertensive and lipid-lowering medication doses as well as exercise levels remained the same throughout the study.
Both dietary patterns resulted in improvements in the CVD risk profile as a consequence of weight loss
A HP diet resulted in greater reductions in total and abdominal fat mass in women and greater LDL-c reduction in both sexes, and suggest it is a valid diet choice for reducing CVD risk in type 2 diabetes.
Industry: |
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- 18% dropout rate
- Demographics of subjects not well described
- The strengths of this study include dietary compliance measures, consideration of a number of covariates/confounders, and multivariate analyses (e.g.: comparison of outcomes by sex/diet).
- Because the energy increase in protein was compensated for by a reduction in carbohydrate, it's not possible to determine if higher protein or lower carbohydrate produced the significant changes.
- Power calculations were not provided, so it may be that there were not enough subjects
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? | ??? | |
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? | ??? | |
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) | Yes | |
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? | ??? | |
4.1. | Were follow-up methods described and the same for all groups? | ??? | |
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? | ??? | |
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? | 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)? | Yes | |
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 | |