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Vegetarian Nutrition

VN: Therapeutic Vegetarian Diets and Attrition (2009)

Citation:

Burke LE, Styn MA, Steenkiste AR, Music E, Warziski M, Choo J. A randomized clinical trial testing treatment preference and two dietary options in behavioral weight management: preliminary results of the impact of diet at six months: PREFER study. Obesity (Silver Spring). 2006 Nov; 14 (11): 2,007-2,017.

PubMed ID: 17135618
 
Study Design:
Randomized Controlled Trial
Class:
A - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:

To evaluate the impact of the interaction between diet type as part of the standard behavior therapy and treatment preference on weight loss at eighteen months.

Inclusion Criteria:
  • 18 to 55 years of age
  • Body mass index (BMI) between 27 and 43
  • Willingness to be randomized to one of two treatment groups: Standard behavior therapy or standard behavior therapy with ovolactovegetarian education
  • Successfully complete a five-day food diary.
Exclusion Criteria:
  • Serious illness or unstable condition for which physician supervision of diet and exercise prescription was needed
  • Cardiovascular or orthopedic condition that would require physician clearance before participation
  • Limited exercise capabilities
  • Pregnant or intending on becoming pregnant in the next 18 months
  • Current treatment for psychological disorder
  • Reported alcohol consumption of greater than four drinks per day
  • Concurrent or previous participation in a weight loss treatment program or used weight loss medication
  • Reported no regular intake of meat, fish and fowl
  • History of serious binge eating problems
  • Did not at least moderately prefer one of the dietary treatments (standard behavior therapy or standard behavior therapy with ovolactovegetarian component) over the other.
Description of Study Protocol:

Recruitment

  • Contacting individuals seeking weight loss treatment and listed in the University of Pittsburgh's Obesity Nutrition Research Center database
  • Placing an audio advertisement on the University and Medical Center's Audix announcement systems
  • Mailing recruitment cards to individuals on purchased address lists.

Design

Initial subjects were screened for eligibility by phone. If the subject met criteria, he or she received a screening packet in the mail. Once the packet was completed the subject was invited to an information session and baseline assessment in which subjects were given a five-day food diary to complete. Upon return of the diary and meeting all the inclusion criteria, the subjects were randomized into the study. 

Diet

During randomization, subjects were initially randomized to treatment preference "yes" or "no" with a three-to-two probability. After this, the subjects were randomized again into either the standard behavior treatment or standard behavior treatment with ovolactovegetarian component. All subjects were instructed to restrict consumption of calories (1,200 to 1,500 for women and 1,500 to 1,800 for men) and fat (25% of total calories). Subjects in the ovolactovegetarian group were asked to record the number of meat meals eaten every day. 

Behavioral Therapy

Subjects received 32 treatment sessions of standard cognitive behavioral therapy for weight management over a period of 12 months, including: Self-monitoring eating and exercise behaviors, goal setting, cognitive restructuring, stimulus control, demonstrations and skill development. The sessions were identical except for information on the two dietary plans. 

Physical Activity

It was recommended to the subjects to increase physical activity to 150 minutes per day. [Note: Article later states physical activity recommendation of 150 minutes per week.]

Subjects were instructed to record their daily food intake and physical activity in minutes and these diaries were used as indicators of adherence to the intervention protocol along with attendance at the treatment sessions.

Laboratory and Physical Assessments

Laboratory assessments included lipid profile, serum glucose and insulin measurement (taken at baseline, six, 12 and 18 months). Physical measurements included height, weight, waist circumference and blood pressure. Subjects were weighed before each treatment session.

Intervention

Standard behavior therapy with an ovolactovegetarian diet.

Statistical Analysis

Only data from baseline to six months is included in the article. To assess differences between the dietary treatment groups and between standard behavior therapy with ovolactovegetarian component groups, chi squared tests were performed for categorical data. For continuous variables, T-tests were used for normally distributed variables and Mann-Whitney tests were used when the variables were not normally distributed.

Data Collection Summary:

Timing of Measurements

Outcome variables were measured at baseline and at six, 12 and 18 months. Treatment sessions were held weekly for the first six months, then every two weeks for months seven to nine and monthly for months 10 to 12. At 12 months, subjects entered the maintenance phase until the 18-month assessment appointment. 

Dependent Variables

  • Anthropometric measurements (weight, waist circumference, blood pressure)
  • Blood serum values (total cholesterol, HDL, LDL, triglycerides, serum glucose and insulin). 

Independent Variables

  • Standard Behavior Treatment
  • Standard Behavior Treatment in conjunction with ovolactovegetarian diet.

 

Description of Actual Data Sample:
  • Initial N: 200 at randomization
  • Attrition (final N): 182 (91%)
  • Age: Average age, 44.1±8.6 years
  • Ethnicity: Mainly Caucasian, though sample had 29.7% minority representation
  • Other relevant demographics: Only 12.6% of subjects were men
  • Anthropometrics: Baseline weight average 94.86kg±14.58kg
  • Location: Pittsburgh, Pennsylvania.
Summary of Results:
  • All subjects who preferred ovolactovegetarian diet were assigned to that group
  • Only fifty percent of those who chose the standard behavior treatment were randomly selected for inclusion
  • Guiding the participants in adopting the ovolactovegetarian diet took many forms, including slow elimination of meat over the first six weeks of the study.  

Changes from Baseline to Six Months

For the entire sample, significant changes were observed at six months in all measures except LDL-C and glucose. Comparing diet groups:

  • Vegetarian diet subjects had significantly lower protein intake (P<0.001) and significantly higher carbohydrate intake (P=0.013) compared to the omnivore diet
  • LDL-C levels were significantly different between diet groups at six months (see table below). 

Baseline and Change Measurements and Comparisons of Change Scores by Diet Group after Six Months

Variables

Standard Behavior Treatment
(Baseline)

Standard Behavior Treatment and Ovolacto-vegetarian
(Baseline)

Standard Behavior Treatment Change
(Change at Six Months)

Standard Behavior Treatment and Ovolacto-vegetarian Change
(Change at Six Months)

Statistical Significance of Different Diets

Weight (kg)

 95.25±14.94

 94.40±14.23

 -0.97±6.53

 -7.50±6.00

NS

Body Mass Index

 34.08±4.24

34.09±3.94
-2.83±2.07
-3.21±2.06

NS

Men: Waist Circumference

111.14±11.12
114.02±10.57
-11.78±10.61
-9.37±5.60
NS

Women: Waist Circumference

103.96±13.47
104.16±12.97
-5.50±6.31
-6.12±7.34
NS

Mean Energy Consumed (calories)

2,053.67±647.79
2,023.76±660.66
-519.80±533.15
-535.98±511.81
NS

Total Cholesterol (mM)

5.29±0.97
5.29±1.06
-0.09±0.63
-0.22±0.66
NS

HDL (mM)

 1.40±0.32

 1.34±0.31

 -0.06±0.18

 -0.04±0.19

NS

LDL (mM)

3.18±0.88
3.27±0.94
0.05±0.55
-0.16±0.54
P=0.013

Triglycerides (mM)

1.54±0.86
1.48±0.71
-0.17±0.61
-0.05±0.66
NS

Glucose (mM)

5.28±0.44
5.35±0.47
-0.03±0.40
-0.06±0.54
NS

Insulin (pM)

127.68±63.60
132.07±59.46
-22.00±39.75
-29.67±40.35
NS

Sex (male) and marital status were the only demographic characteristics significant with compliance in the standard behavior treatment with ovolactovegetarian component.

Baseline and Change Measurements and Comparisons of Change Scores of the Ovolactovegetarian Participants by Adherence Group after Six Months

Variables

100% Adherence
(Baseline)

<100% Adherence
(Baseline)

100% Adherence
(Change at Six Months)

<100% Adherence
(Change at Six Months)

Statistical Significance of Different Diets

Weight (kg)

 94.05±14.45

90.45±12.73

 -10.63±5.39

 -4.98±3.95

<0.001

Body Mass Index

 34.02±4.02

34.01±4.20
-3.87±1.99
-1.91±1.59

<0.001

Men: Waist Circumference

113.44±11.04
 
-11.60±4.34
 
 

Women: Waist Circumference

105.14±12.39
101.86±13.31
-8.84±8.21
-4.25±4.96
0.018

Mean Energy Consumed (calories)

 
2,076.09±614.95
 
1,930.30±709.75
--696.47±481.29
-512.00±516.13
NS

Total Cholesterol (mM)

5.29±1.02
5.25±1.13
-0.38±0.76
0.02±0.54
0.026

HDL (mM)

 1.34±0.31

 1.27±0.27

 -0.05±0.20

 -0.02±0.22

NS

LDL (mM)

3.25±0.96
3.27±0.94
-0.28±0.60
0.03±0.49
0.034

Triglycerides (mM)

1.53±0.77
1.55±0.67
-0.10±0.85
0.03±0.35
NS

Glucose (mM)

5.48±0.47
5.15±0.43
-0.22±0.41
0.20±0.78
0.002

Insulin (pM)

138.78±64.55
125.53±51.35
-38.57±40.46
-27.23±44.44
NS

Author Conclusion:

Subjects in both diet groups benefited from the first six months of the behavioral intervention in that they reduced their weight by greater than 7%, which results in clinically significant improvements. Subjects who were adherent to the ovolactovegetarian diet experienced significant improvements in several physical and biological outcome measures.

Funding Source:
Other: No funding sources acknowledged
Reviewer Comments:
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
  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
  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
  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
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
 
Validity Questions
  1. Was the research question clearly stated? Yes
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.1. 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
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
  1.3. Were the target population and setting specified? Yes
  2. Was the selection of study subjects/patients free from bias? 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
  2.1. 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
  2.2. Were criteria applied equally to all study groups? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? 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
  2.4. Were the subjects/patients a representative sample of the relevant population? Yes
  3. Were study groups comparable? 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) No
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) No
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? 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
  3.3. 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
  3.4. 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
  3.5. 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
  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. Was method of handling withdrawals described? Yes
  4.1. Were follow-up methods described and the same for all groups? 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
  4.2. 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
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? ???
  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
  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. 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? 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
  5.2. 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
  5.3. 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
  5.4. 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
  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. 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
  6.1. 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
  6.2. 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
  6.3. 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
  6.4. 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
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? Yes
  6.6. Were extra or unplanned treatments 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
  6.7. 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
  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. 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
  7.1. 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
  7.2. 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
  7.3. 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
  7.4. 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
  7.5. 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
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  7.7. Were the measurements conducted consistently across groups? 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. 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
  8.1. 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
  8.2. 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
  8.3. 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
  8.4. 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
  8.5. 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
  8.6. 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
  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. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? 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. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes
  10.2. Was the study free from apparent conflict of interest? Yes