National Coverage Determination (NCD)


Dengel DR, Kelly AS, Olson TP, Kaiser DR, Dengel JL, Bank AJ. Effects of weight loss on insulin sensitivity and arterial stiffness in overweight adults. Metabolism 2006; 55: 907-911.

PubMed ID: 16784962
Study Design:
Before-After Study
D - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:

To assess the effects of six months of energy restriction on insulin sensitivity, detailed measures of arterial endothelial function and wall mechanical properties in middle-aged, overweight and obese adults.

Inclusion Criteria:
  • Overweight and obesity (BMI=30.3±3.7)
  • Sedentary
  • No hypertension, dyslipidemia, impaired fasting glucose, or history of cardiovascular, peripheral vascular or cerebral vascular disease.
Exclusion Criteria:
  • Body weight of more than 200% of the ideal
  • Significant underlying medical illness
  • Use of medications known to alter vascular or metabolic function.
Description of Study Protocol:


Voluntary overweight and obese subjects were recruited from the Minneapolis-St. Paul Metropolitan area. 


Before-After Study. Subjects were counseled by a registered dietitian in a behavioral modification or weight program one time per week for six months. Participants were counseled to restrict food intake by 300 to 500kcal per day. Adherence was monitored by a review of day-by-day food records and meeting with subjects weekly. Anthropometric and biochemical parameters, as well as the assessment of vascular structure and function were analyzed.

Blinding used

Not applicable 


Weight-reduction program with a dietitian 

Statistical Analysis

Paired Student T-test and repeated-measures analysis of variance were used to determine the effect of weight loss on each of the variables. A P-value of less than 0.05 was considered statistically significant.


Data Collection Summary:

Timing of Measurements

Body composition, assessment of vascular structure and function, assessment of insulin sensitivity and blood pressure were measured at baseline and after six months of intervention. Blood lipids profile were measured at baseline and within one week of the final dietitian-guided meeting. 

Dependent Variables

  • Body Weight (kg
  • Lean body mass (kg)
  • Fat mass (kg)
  • Percentage of body fat
  • Total cholesterol (mmol/L)
  • LDL-cholesterol (mmol/L)
  • HDL-cholesterol (mmol/L)
  • Triglycerides (mmol/L)
  • Fasting glucose (mmol/L)
  • Fasting insulin (pmol/L)
  • Blood pressure (mm Hg)
  • Brachial artery FMD (percentage)
  • Brachial and Carotid artery wall CSA
  • Brachial and Carotid artery IMT (mm).

Independent Variables

Behavioral modification-weight loss program with restriction of food intake between 300 to 500kcal per day. 

Control Variables


Description of Actual Data Sample:

Initial N 

12 (three males, nine females)

Attrition (final N)

12 (three males, nine females)


50 to 65 years, mean age: 54.9±3.9 years


Not mentioned

Other relevant demographics

None of the women were using hormone replacement therapy



University of Minnesota, Minneapolis, Minnesota.


Summary of Results:

 Clinical characteristics before and after weight loss

  Before weight loss After weight loss P
Body weight (kg) 86.3±4.1 79.5±4.0 0.0003
Lean body weight (kg) 46.5±27.3 45.0±26.9 0.04
Fat mass (kg) 37.1±25.9 27.9±30.8 0.02
Percentage of body fat 44.3±2.0 41.0±2.5 0.003
Total cholesterol (mmol/L) 6.0±0.3 5.0±0.2 0.0001
LDL-C (mmol/L) 3.9±0.2 3.2±0.2 0.0001
HDL-C (mmol/L) 1.4±0.1 1.4±0.1 0.26
Triglycerides (mmol/L) 1.5±0.3 1.1±0.1 0.06
Fasting glucose (mmol/L) 5.4±0.1 5.3±0.1 0.32
Fasting insulin (mmol/L) 12.1±0.7 10.6±0.7 0.52

Other Findings

  • There was a 63.6% improvement of insulin sensitivity from baseline to after weight loss (3.3±0.5 vs. 5.4+0.5 μU x 10-4 min-1 mL-1, P<0.000)
  • There were no significant changes in brachial and carotid artery diameter, intima-media thickness, wall cross-sectional area as a result of the weight loss intervention
  • Brachial artery pressure-area, compliance and distensibility curves over the physiologic pressure range improved, P<0.05.


Author Conclusion:

In overweight adults, six months of weight loss improves body composition, insulin sensitivity and arterial wall mechanical properties with positive changes in other metabolic and lipid parameters.

Funding Source:
Government: NCRR/NIH;Department of Veterans Affairs VA Merit Award
Reviewer Comments:

Small sample size and lack of a control group are the limitations recognized by the authors.

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? N/A
  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.) N/A
  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%.) N/A
  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? Yes
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? ???
  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? N/A
  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)? No
  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? 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