EAL

DM: Prevention and Treatment of CVD (2007)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To investigate the effects of a short-term dietary intervention on lipids, hormones, and metabolic control in patients with type 2 diabetes and hypertriacylglycerolemia.

Inclusion Criteria:

type 2 diabetes as defined by clinical criteria
age 40-75 y
fasting triacylglycerol greater-than-or-equal-to 2.2 mmol/l

Exclusion Criteria:

insulin treatment
proliferative retinopathy
pregnancy or lactation
grade III or IV heart failure
allergy to fish, or other ailment prohibiting diet intervention
alcoholism or other serious diseases affecting the subjects' possibilities of participating in the study

Description of Study Protocol:

Recruitment : recruited from an outpatient endocrinological clinic

Design: Nonrandomized Clinical Trial

food intake at usual diet was recorded during two separate 3-day periods 2-5 weeks apart
during a third 3-day period subjects consumed a low-fat intervention diet
the second 3-day recording period of usual intake was used for baseline dietary data (taken 2-3 weeks before intervention period)

Blinding used (if applicable): none

Intervention (if applicable):

during the three dietary periods, food and beverages were weighed on an electronic kitchen scale; subjects weighed their own food after practice under the supervision of one of the investigators
intervention diet was low-fat and fiber-rich and intended to be isoenergetic with the usual diet
subjects were told to reduce all visibile fats, increase their intake of cereals, whole-meal breads, potatoes, rice, pasta, fish, vegetables, and fruits.
subjects were told to eat the same amounts of dairy and meat products as usual, but low-fat variations

Statistical Analysis

results given as median values with the variability shown as Inter Quartile Range (distnace between the 75th and 25th percentiles
significance testing included the paired Wilcoxon signed ranks test
distances between medians wee tested with the unpaired Mann-Whitney test
Spearman's correlation coefficients were used to evaluate bivariate correlation

Data Collection Summary:

Timing of Measurements: fasting variables obtained on the morning following the 3 days of dietary intervention

Dependent Variables

leptin
adiponectin
insulin
glucagon
C-peptide
proinsulin
cortisol
free fatty acids (FFA)
plasma phospholipid fatty acids (PL-FA)
glucose
triacylglycerol
cholesterol
HDL
HbA1c

Independent Variables

dietary intake

Control Variables

Description of Actual Data Sample:

Initial N: 19

Attrition (final N): 19

Age: median 62, IQR 17

Ethnicity: not specified

Other relevant demographics:

median duration of diabetes 7 years with IQR of 5 years
HbA1c at baseline: median 8.0, IQR 2.1
triglycerides at baseline: median 2.6, IQR 1.7

Anthropometrics:

waist circumference: median 103, IQR 21
BMI: median 30.1, IQR 6.5

Location: Norway

Summary of Results:

Dietary Intake

baseline diet was 17% protein, 39% fat, and 41% carbohydrate
after 3 days on the low-fat diet median intakes were significantly different (all at p<0.001)
- protein 22.3%
- fat 24.3%
- carbohydrate 50.6%

Variables	After intervention: change in values from baseline		Statistical Significance of Group Difference
	Median	Inter Quartile Range
Glucose, mmol/l	-0.6	1.1	*
Insulin, mU/l	-0.6	7.5
HOMA, %	0	30
Glucagon, pmol/l	1	15
Proinsulin, pmol/l	1	5
C-peptide, mmol/l	-0.1	0.2
Cortisol, nmol/l	-54	239
Leptin, ng/ml	-1.7	3.8	**
Adiponectin, microgram/l	1.1	3.4	*
total cholesterol, mmol/l	-0.5	0.6	**
HDL,mmol/l	-0.05	0.08	*
Triacylglycerols, mmol/l	-0.1	0.7
FFA, mmol/l	0.04	0.32
PL-FA, mmol/l	-14	166
SFA, g/100g PL-FA	-0.5	0.7	***
MUFA, g/100 g PL-FA	0.4	0.8	***
n-6 FA, g/100 g PL-FA	-2.3	3.4	**
n-3 FA, g/100 g PL-FA	2.4	3.3	**
n-6/n-3 ratio	-0.7	0.8	**

*p<0.05

**p<0.01

***p<0.001

Author Conclusion:

A 3-day low-fat diet intervention significantly affected lipid variables and concentrations of leptin and adiponectin but failed to reveal any beneficial effects on insulin sensitivity and metabolic control in insulin-resistant type 2 diabetes.

A low-fat diet with a reduction in saturated fat may still be beneficial with regard to dvelopment of cardiovascular disease.

The short duration of the study rules out effects from successive changes in lifestyle as a result of inclusion in the study.

Funding Source:

Reviewer Comments:

Although the duration of this study was very short, the authors clearly state their reasons for making it so, that is that they wanted to minimize the effects of weight loss, and optimize compliance.

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)	N/A
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	N/A
	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?	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?		Yes
	6.1.	In RCT or other intervention trial, were protocols described for all regimens studied?	N/A
	6.2.	In observational study, were interventions, study settings, and clinicians/provider described?	Yes
	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?	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?	N/A
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?	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