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NC: Cardiovascular Disease Risk Factors (2007-2008)

Citation:

Volek JS, Gómez AL, Love DM, Weyers AM, Hesslink R Jr, Wise JA, Kraemer WJ. Effects of an eight-week weight-loss program on cardiovascular disease risk factors and regional body composition. European Journal of Clinical Nutrition, 2002, 56; 585-592.

 

PubMed ID: 12173568
 
Study Design:
Case control study
Class:
C - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:

The primary purpose of this study was to examine the short-term effects of a weight loss program focusing on reducing percentage energy from fat, increasing exercise and multi-vitamin or mineral supplementation on serum plasma concentrations of CVD risk factors and regional body composition in overweight men and women.

Inclusion Criteria:
  • Healthy
  • No endocrine, orthopedic or other pathological disorders
  • Overweight, body fat greater than 20%.
Exclusion Criteria:

None

Description of Study Protocol:
  • Recruitment: Unknown
  • Design: Subjects participated in an eight-week weight loss program. A comparison control group did not participate in the program.
  • Blinding used: None
  • Intervention: The weight-loss program followed general guidelines for reducing dietary fat and increasing exercise, as well as instruction on behavior modification and nutritional supplementation
  • Statistical analysis: 
    • All data was presented as means and standard deviations
    • Dependent variables were analyzed using a two-way analysis of variance with gender (men vs. women) and time (baseline vs. week eight)
    • When a significant F-value was achieved, a Fisher’s LSD test was used to located the pairwise differences between means
    • Pearson correlation coefficients were used to determine associations between leptin and other variables
    • Statistical power ranged from 0.78 to 0.80 at a P-value equal to 0.05 for the various dependent variables
    • The level of significance was set at P<0.05.
Data Collection Summary:

Timing of Measurements

Initial measurements and at the end of the eight-week program.

Dependent Variables

  • Self-documentation of food and beverage intake, exercise training duration and intensity and daily achievement toward nutritional, exercise and behavioral goals
  • Body composition and circumferences. Body Mass was determined on a calibrated clinical scale. Two circumference measurements were made on the right side of the body. Body composition was obtained by dual-energy X-ray absorptiometry (DEXA) using a total body scanner.
  • Blood collection and analysis: Blood was obtained after a 12-hour overnight fast at the same time of the morning before and after the study.
    • Total cholesterol
    • LDL-cholesterol
    • HDL-cholesterol
    • Triacylglycerols
    • Homocysteine
    • Insulin
    • Leptin.

Independent Variables

  • The weight-loss program followed general guidelines for reducing dietary fat and increasing exercise, as well as instruction on behavior modification and nutritional supplementation
  • Subjects consumed a self-selected diet in a free-living environment
  • Subjects were required to attend weekly group meetings led by an RD.

Control Variables

Eight men were asked not to change their diet or activity patterns for eight weeks.

 

Description of Actual Data Sample:
  • Initial N: 22 (12 women; 10 men)
  • Attrition (final N): None noted
  • Age: Women: 42.4±7.7 years; men 39.7±11.0 years
  • Ethnicity: None noted
  • Other relevant demographics: None noted
  • Anthropometrics: Women: 35 to 57% body fat; men: 20 to 40% body fat
  • Location: The Human Performance Laboratory at the University of Connecticut, Storrs, Connecticut.

 

Summary of Results:

 

Variables

Women (N=12)

Measures and Confidence Intervals

Women (N=12)

Measures and Confidence Intervals

Men (N=10)

Measures and Confidence Intervals

Men (N=10)

Measures and Confidence Intervals

Statistical Significance of Group Difference    

Nutrients

 

Week One        
Week Eight

Week One       

Week Eight

Statistically significant difference between groups (e.g., P=0.002)

Energy          
Protein (grams) 5.74±1.08     4.65±1.39* 7.74±1.60 6.71±1.88*  
Protein (percentage) 57±15 50±13 84±15 74±27  
Carbohydrate (grams) 17±14 18±2 18±2 18±3  
Carbohydrate (percentage) 200±62 152±64* 259±71  242±57  
Fat (grams) 56±9 54±13 55±10  60±6  
Fat (percentage)  40±10 34±17  55±22  41±17  
Saturated fat (grams)  26±7 27±12  26±10 22±5  
Cholesterol (milligrams)  13±5 12±6  17±9 17±7  
Dietary fiber (grams)  160±90 124±100  205±106 134±74  
Folic Acid (microgram)  16±7 12±8*  17±4  15±6  
Vitamin B6 (milligrams)  223±68 183±127  293±149 339±170  
Vitamin B6 (milligrams)  1.2±0.4 1.0±0.4  2.0±0.9 1.9±0.9  
Vitamin B12 (microgram)  2.3±1.4 1.9±1.4   5.2±3.0 4.8±2.2  

Body Composition

Change after eight weeks (Women)

 

Change after eight weeks (Men)

 

Interaction effect (P)

BM kilogram (scale) -4.3±3.4*    -4.7±3.1*   0.795
BM kilogram (DXA)  -3.8±3.3*   -4.2±4.1*   0.825
FFM (kilogram) -1.4±1.7   -0.4±2.6   0.315
FM (kilogram) 2.5±2.4*   -3.7±2.3*   0.209

Percentage of Fat

-1.0±2.0  
 -2.7±1.7
 
0.045

Serum Values

Change after eight weeks (Women)

 

Change after eight weeks (Men)

 

Interaction effect (P)

Total Cholesterol (mg/dl)   -6±18     -18±14*    0.102
LDL Cholesterol (mg/dl)   -4±17    -14±14*    0.135
HDL Cholesterol (mg/dl)  -1±6     1±7    0.525
Triglycerols (mg/dl)  -7±44    -23±72    0.513
Leptin (umol/l)  -16.2±0.8    -3.9±0.6    0.017
Insulin (pmol/l)  4±40*    -4±31    0.603
Homocysteine(umol/l) 0.3±1   0.0±0.9   0.574

*P≤0.05= main effect (baseline vs. week eight)

Other Findings

An additional conclusion reached by these authors is that supplementation with folic acid may be an important component of a weight loss program to prevent increases in homocysteine.

Author Conclusion:

Overweight subjects that made moderate changes in self-selected diet, exercise patterns and supplementation in a free-living environment demonstrated improvements in total and regional body composition and blood lipid profiles.

Funding Source:
Industry:
Natural Alternatives International, San Marcos, California
Food Company:
Reviewer Comments:
  • A short (eight-week) weight loss program that emphasized dietary fat restriction, nutritional supplementation, weekly behavior modification support group meetings and a supervised structured exercise program was able to demonstrate positive changes (in CVD risk factors) in a small group of subjects
  • An additional conclusion reached by these authors is that supplementation with folic acid may be an important component of a weight loss program to prevent increases in homocysteine.

 

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? ???
  2.4. Were the subjects/patients a representative sample of the relevant population? ???
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) ???
  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.) Yes
  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? N/A
  4.1. Were follow-up methods described and the same for all groups? N/A
  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? N/A
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? N/A
  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.) N/A
  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? ???
  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? N/A
  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? 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? 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? 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? 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)? ???
  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