EAL

DM: Weight Management (2001)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To determine the effect of energy restriction and fat loss on serum lipids in obese subjects with and without type 2 diabetes mellitus.

Inclusion Criteria:

1. Mild obesity (BMI = 31.5 ±0.8 kg/m²)

2. Consumed <20g of alcohol per day

3. Considered by a dietitian to be motivated to lose weight

4. Not gone on a diet in the past 6 months

Exclusion Criteria:

Subjects with a history of endocrine, cardiac, hepatic or renal disease

Description of Study Protocol:

Recruitment: Recruited from a diabetic clinic and through advertisements (9 subjects with normal glucose tolerance (NGT) and no family history of diabetes; 9 subjects with type 2 diabetes mellitus).

Design: Nonrandomized Clinical Trial.

Blinding Used: Not used

Intervention (if applicable):

Subjects either with type 2 diabetes or normal glucose tolerance on a customized formula diet for four weeks.

Statistical Analysis: Baseline characteristics of the two groups were compared by unpaired t test. Anthropometric changes over the whole study were assessed using paired t test. The effects of energy restriction versus weight loss were assessed by t test. All results are expressed as means + SEM.

Data Collection Summary:

Timing Of Measurements:

lipid levels were measured before and on the 4th and 28th days of the diet.
body composition assessed on the day before the study and on day 28.

Dependent Variables:

serum lipids
total body fat and abdominal fat assessed through DEXA

Independent Variables:

Subjects either with type 2 diabetes or normal glucose tolerance on a customized formula diet for four weeks.
Before the energy restricted diet began, subjects were assessed for dietary composition (assessed by a dietitian from 4-day food records), weight, anthropometry, body composition, and fasting lipid levels.
Each subject was supplied with a customized formula diet for 4 weeks based on body size, age, and energy intake to decrease intake by 1000 kcal/day (per 100g: protein = 37g, fat 2.3g (PUFA 9%, MUFA 30%, saturated fat 61%), carbohydrate = 40g, energy content = 330 kcal), supplemented with EFA's and minerals

Description of Actual Data Sample:

Initial N: 18 subjects. 9 with type 2 diabetes and 9 with normal glucose tolerance (NGT).

Attrition (Final N): 14. Data from 2 NGT subjects were excluded because of technical difficulties during the clamps. One subject with diabetes was excluded because of recommencement of sulphonylurea therapy toward the end of the diet. A second diabetic subject was excluded from analysis of changes in body composition because of technical problems during the final dual energy X-ray absorptiometry (DXA) scan.

Age: NGT: 48.4 + 3.6 years, Type 2 diabetes: 47.6 + 4.8

Ethnicity: Not mentioned

Other Relevant Demographics: Gender (M:F): 5:4 NGT, 4:5 type 2 diabetes, BMI: (kg/m²): 31.5 + 0.8 NGT, 31.8 + 0.7 type 2 diabetes

Anthropometrics: Baseline characteristics were not statistically significant between groups

Location: Sydney, Australia

Summary of Results:

Dietary composition:

There was a significant reduction in intake of all macronutrients in absolute terms and about a 50% reduction in energy intake (P = 0.0001)

Prediet:

Energy: 2,300 ±170 kcal
CHO: 38.4 ±1.8%
Protein: 19.2 ±0.7%
Fat: 35.7 ±1.2%
- PUFA: 5.9 ±0.4%
- MUFA: 13.8 ±0.6%
- SF: 16.1 ±0.6%
Alcohol: 6.8 ±2.1%
Fiber: 26 ±2g

Diet:

Energy: 1,100 ±60 kcal
CHO: 38.3 ±0.7%
Protein: 32.6 ±0.8%
Fat: 28.8 ±0.8%
- PUFA: 10.1 ±0.5%
- MUFA: 11.9 ±0.4%
- SF: 6.0 ±4%
Alcohol: 1.3 ±0.8%
Fiber: 9 ±1g

Anthropometric changes:

	Prediet	Postdiet (d28)	P value
Weight (kg)	95.9 + 2.7	89.9 + 2.6	0.0001
BMI (kg/m²)	31.7 + 0.5	29.6 + 0.5	0.0001
Waist Circumference (cm)	98.3 + 2.3	92.6 + 2.1	0.0001
WHR	0.88 + 0.02	0.86 + 0.02	0.002
Skinfold thickness (% fat)	34.6 + 1.6	33.0 + 1.6	0.0003
Total fat DXA (%)	38.6 + 2.2	37.8 + 2.3	0.03
Abdominal fat DXA (%)	42.9 + 1.3	40.9 + 1.6	0.01
Abdominal fat DXA (g)	2,700 + 100	2,400 + 100	0.0001

d4: 1.8 ±0.3 kg loss of initial wt.
d28: 6.2 ±0.4 kg loss of wt.
A significant amount of weight was lost from the abdominal region compared to that of total body fat loss (P = 0.004)
Abdominal fat: 14 ±2% decrease
Total body fat: 8 ±1% decrease

Lipid changes:

d4: Significant changes were observed in total TG, LDL particle size, and VLDL cholesterol levels.
d28: After fat loss, significant decreases were apparent in total and LDL cholesterol and LDL TG; there was also a significant decrease in LDL apoB, which was not measured at d4.

Lipid and body compositional changes:

d0: Significant association between abdominal fat and total TG and esterified LDL cholesterol.
d28: Loss of abdominal fat was the only change that related significantly to changes in the lipid profile (strongly associated with a decrease in LDL free cholesterol (P = 0.006) and LDL apoB (P = 0.008).

Author Conclusion:

Both energy restriction and fat loss improve serum lipid levels in mildly obese subjects, independently of type 2 diabetes. Energy restriction was associated with a decrease in TG-related factors in association with an improvement in hepatic insulin action. Loss of abdominal fat was associated with an improvement in LDL free cholesterol and LDL apoB levels independent of total fat loss. This study clarifies the effects of energy restriction and fat loss and demonstrates how dietary intervention can improve the lipid profile in mildly obese subjects at risk of atherosclerotic vascular disease.

Funding Source:

Government:

national health and medical research council of australia

Reviewer Comments:

Since study was conducted for only one month, it would be interesting to see results over a longer period of time. Small amount of subjects in each group.

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)	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?		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?	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.)	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?	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?	No
	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)?	Yes
	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?	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