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NC: Behavior Change Strategies (2007-2008)

Citation:

Metz JA, Kris-Etherton PM, Morris CD. Dietary compliance and cardiovascular risk reduction with a prepared meal plan compared with a self-selected diet. Am J Clin Nutr. 1997; 66: 373-385.

 
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:

The purpose of this study is to compare the dietary compliance and CVD risk factor response in two dietary interventions designed to treat hypertension, dyslipidemia, and diabetes mellitus.

Inclusion Criteria:
  1. 25 to 70 years of age
  2. Body Mass Index up to 42
  3. One or more of the following criteria:
    • Hypertension: Taking no anti-hypertensive medications and average systolic BP 140mm to 180mm hg, sitting diastolic BP 90mm to 105mm Hg, or both or stabilized through use of anti-hypertensive medications for at least one month before the study and average sitting systolic BP of 135-180mm Hg or diastolic BP 85mm to 100mm Hg
    • Dyslipidemia: Taking no lipid-lowering medications and total cholesterol concentration of 220mg 300mg per dL, triacyglycerol concentration of 200mg 1,000mg per dL, or both or stabilized through use of lipid-lowering medications for at least one month before study and a cholesterol concentration of 200mg to 260mg per dL, triacylglycerol contration of 200mg to 1,000mg per dL or both
    • NIDDM: Taking no hypoglycemic agents, fasting blood glucose concentration over 140mg per dL and glycated hemoglobin (HbA1c) concentration up to 15.4% or stabilized through use of oral hypoglycemic agents for at least one month before study with HbA1c concentrations 7.7% to 13.4%
    • A combination of disorders: Meet the criteria for more than one of the above categories.
Exclusion Criteria:
  1. Does not meet the above inclusion criteria
  2. Life-threatening diseases
  3. Receiving insulin treatment
  4. Pregnant or not practicing birth control
  5. Substance or alcohol abuse
  6. Refusal to discontinue vitamin-mineral supplements.
Description of Study Protocol:

Recruitment

Subjects were recruited at 10 different clinical centers around the United States.

Design

  • All subjects were initially enrolled in a baseline period (Weeks Four through Zero) and advised to maintain their usual diets and seen weekly for blood pressure and weight measurements. They were instructed on completing three-day food records and two of these were collected during this period. A physical exam was conducted and fasting blood was collected to measure chemistry profile, HbA1c and lipid and lipoproteins. Participants were asked to maintain their usual physical activity levels.
  • At Week Two, a nutrition prescription was calculated for each patient using Harris-Benedict equation. Calculations were made with the goal of limiting weight loss to one kg per week and a total of 11kg for the intervention.
  • At Week Two, subjects were randomly assigned by the coordinating center to either the prepared meal plan or self-selected diet group; stratified by four diagnostic categories (hypertension, dyslipidemia, NIDDM or combination of above) and clinic site.
  • Subjects consumed either the prepared meal plan or the self-selected meals for 10 weeks. They were seen every two weeks for measurements of BP, weight and collection of three-day food record. Fasting blood was collected at weeks zero and 10 for the measurements described above, at week four for glucose and lipoproteins and again at week eight for lipoproteins.

Intervention

  • At Week Zero, all participants were counseled regarding their assigned therapeutic diet and were provided with educational materials to help them adhere to their program for the 10-week intervention.
  • The prepared meals were produced by the Campbell Soup Company and included six breakfast, eight lunch, 10 dinner and six snack selections. Meals were ordered by participants at clinic visits and the foods were delivered to their homes. Participants were instructed to consume one serving each day of the breakfast, lunch, and dinner entrées and to include one serving daily of fruit, vegetables and low-fat dairy products.
  • Participants in the self-selected diet group were prescribed a specific number of servings from each of the ADA exchange lists that were congruent with providing 15-20% of energy from fat, 55-60% from carbohydrate and 15-20% from protein. The self-selected diet closely resembled the National Cholesterol Education Program and American Heart Association Step 2 Diet.

Statistical Analysis

  • The study was designed to detect differences between treatment groups of three mm Hg in BP, 10mg per dL in plasma cholesterol, 20mg per dL in triacylglycerols, 10mg per dL in plasma glucose and a 1% difference in HbA1c. With a power of ≥ 80% and a two-sided alpha of 0.05, these differences were detectable with a sample of 80 in each group based on variation as defined in a preliminary study. 
  • A repeated measures analysis of variance model was used to analyze differences between baseline and treatment periods.
  • Changes in nutrient intake from baseline to treatment were analyzed by using analysis of repeated measures.
  • For analysis of the proportion of participants meeting dietary compliance criteria, and the compliance-end-point responses, chi-square tests were used to detect independence of categorical factors.

 

Data Collection Summary:

Timing of Measurements

Subjects were seen every two weeks for measurements of BP, weight and collection of three-day food record. Fasting blood was collected at weeks zero and 10 for the measurements described above, at week four for glucose and lipoproteins and again at week eight for lipoproteins. Three-day food records were collected at weeks two, four, six, eight and 10.

Dependent Variables

Variable One: Dietary Compliance, assessed from three-day food records by evaluating the ability of participants to meet specific dietary criteria for intakes of energy from total fat and the NCEP/AHA Step 1 and 2 dietary recommendations. Baseline nutrient intakes were estimated by averaging nutrient intake from two three-day food records collected over the course of the study.

  • 1a: Energy (kcal): Determined by calculating the difference between reported energy intake and the midpoint of the prescribed energy range
  • 1b: Protein (g)
  • 1c: Carbohydrate (g)
  • 1d: Total Fat (g): The fat composition of both diets averaged 17% and this was used as an index of compliance.
  • 1e: Energy from fat (percentage)
  • 1f: Energy from protein (5)
  • 1g: Energy from carbohydrate (percentage)
  • 1h: Energy from SFA (percentage)
  • 1j: Energy from PUFA (percentage)
  • 1k: PUFA (g)
  • 1l: Energy from MUFA (percentage)
  • 1m: MUFA (g)
  • 1n: Cholesterol (mg)
  • 1o: Calcium (mg)
  • 1p: Fiber (g)
  • 1q: Potassium (mg)
  • 1r: Sodium (mg)
  • 1s: Magnesium (mg)
  • 1t: Folate (microgm).

Variable Two: Changes in study endpoints

  • 2a: Sitting systolic BP (mm Hg): Determined in accordance with recommendations of the AHA
  • 2b: Sitting diastolic BP (mmg Hg)
  • 2c: Cholesterol (mmol/L): Plasma lipoproteins determined at the Northwest Lipid Laboratories, University of Washington. T-Chol measured by the colorimetric enzymatic endpoint method
  • 2d: Triaclyglycerol (mmol/L)
  • 2e: LDL (mmol per L): Calculated by using the Friedewald algorithm
  • 2f: HDL (mmol per L): Analyzed by the heparin-manganese method
  • 2g: VLDL (mmol per L)
  • 2h: Insulin (pmol per L): Measured by using a solid phase radio-immunoassay at the Hormone and Mineral laboratory, Oregon Health Sciences University
  • 2i: Weight (kg)

Independent Variables

  1. Prepared meal plan
  2. Self-selected diet.

 Control Variables

  1. Three-day food records with instruction for completion
  2. Nutrition prescription calculated using Harris-Benedict Equation to estimate individual energy needs
  3. Educational material and verbal instruction on following prescribed diet plans. Dietary counseling provided to all subjects by study nutritionists.
Description of Actual Data Sample:

Initial N

  • 560
  • Prepared meal plan: 283
  • Self-selected diet: 277.

Attrition (Final N)

  • Prepared Meal Plan Group: N=272 (92%)
  • Self-Selected Diet Group: N=270 (97%).

Demographics

Demographics            

Prepared Meal Plan N=114 

Prepared Meal Plan Women N=169

Self Selected Diet Men N=132

Self-Selected Diet Women N=145

Age (years)

55±10

54±10

53±9

54±9

Race (percentage)

White

84

85

86

83

African-American

13

9

8

11

Other

3

6

6

6

BMI (kg/m2)

31±4

31±5

31±4

31±5

Current Smokers (percentage)

16

9

12

10

Alcohol Intake (percentage)

56

48

62

54

Education (years)

15.0±3.0

14.2±2.7

14.9±3.0

13.8±2.5

Other Significant Demographics

In the dyslipidemia group, there were more African-American and Hispanic participants in the self-selected diet group.

Summary of Results:

Changes in reported daily nutrient intakes in study participants stratified by sex and treatment group from baseline to end of treatment.1

Women                    

Variables

Prepared Meal Plan

Baseline (N=169 W, 114 M)

Prepared Meal Plan

Treatment (N=163 W, 109 M)

Prepared Meal Plan

Change N=163 W, 109 M)

Self-Selected Diet        

Baseline (N=145 W, 132 M)

Self-Selected Diet 

Treatment (N=142 W, 128 M)

Self-Selected Diet

Change (N=142 W, 128 M)

Energy (kcal)

1,772±460

1,436±288

-327 1,768±494

1,386±323

-387

Protein (grams)

74±18

72±11

-13 72±19

67±15

-6

Carbohydrate (grams)

227±65

217±43

-10 217±65

201±51

-17
Total Fat (grams) 65±25 29±11 -35 69±27 37±15 -31
Energy from fat (percentage) 32±7 18±3 -143 34±6 24±6 -10
Energy from Protein (percentage) 17±3 20±2 3 17±3 20±3 3
Energy from Carbohydrate (percentage) 52±8 61±4 9 49±7 58±6 9
Energy from SFA (percentage) 10.9±3.0 6.2±1.3 -4.73 11.4±2.8 7.5±2.1 -3.8
Saturated Fat (grams) 22±10 10±4 -12 23±10 12±5 -11
Energy from PUFA (percentage) 6.6±1.94 4.6±0.7 -2.0 7.2±2.04 5.2±1.7 -2.0
PUFA (grams) 13.2±5.6 7.4±2.5 -6 14.2±6.1 8.1±3.3 -6
Energy from MUFA (percentage) 12.2±3.1 6.3±1.5 -5.93 13.1±2.7 8.9±2.6 -4.1
MUFA (grams) 25±10 10±4 -14 26±11 14.2±6.1 -12
Cholesterol (mg) 219±107 104±47 -1093 226±105 146±61 -79
Calcium (mg) 787±297 1,726±295 9373 730±245 801±242 69
Fiber (grams) 19.2±7.3 30.4±5.4 11.23 18±6.0 20.9±6.4 2.8
Potassium (mg) 2,748±754 3,980±662 1,2293 2,649±621 2,909±718 241
Sodium (mg) 3,110±947 2,274±462 -7903 3,049±971 2,697±758 -352
Magnesium (mg) 291±80 573±91 2823 277±72 290±74 12.1
Folate (ug) 275±105 649±113 3743 254±82 306±98 49
  

Men

Variables

Prepared Meal Plan

Baseline (N=169 W, 114 M)

Prepared Meal Plan

Treatment (N=163 W, 109 M)

Prepared Meal Plan

Change N=163 W, 109 M)

Self-Selected Diet        

Baseline (N=145 W, 132 M)

Self-Selected Diet 

Treatment (N=142 W, 128 M)

Self-Selected Diet

Change (N=142 W, 128 M)

Energy (kcal)

2,222±6224

1,849±388

-4775 2,492±7414

1928±421

-4593

Protein (grams)

92±254

86±15

-105,6 102±314

92±20

-65

Carbohydrate (grams)

267±86

287±60

-203 291±314

270±69

-18
Total Fat (grams) 87±334 37±14 -565,6 101±284 55±19 -405
Energy from fat (percentage) 37±7 18±3 -173 36±7 26±7 -10
Energy from Protein (percentage) 17±3 19±2 23 17±3 19±3 3
Energy from Carbohydrate (percentage) 48±8 62±4 143 47±8 56±7 9
Energy from SFA (percentage) 11.5±2.9 6.3±1.1 -5.13 11.9±2.9 8.2±2.7 -3.7
Saturated Fat (grams) 29±124 13±5 -185,6 34±14 4 18±7 -145
Energy from PUFA (percentage) 7.0±2.0 4.5±0.7 -2.5 7.3±2.1 5.3±1.4 -2.0
PUFA (grams) 17.4±8.04 9.2±2.8 -105,6  20.5±9.54 11.4±3.8 -85
Energy from MUFA (percentage) 13.5±3.0 6.1±1.3 -73 13.8±2.9 9.7±2.8 -4
MUFA (grams) 34±134 13±5 -235,6 39±154 21±8 -165
Cholesterol (mg) 310±136 114±51 -1935,6 347±156 219±82 -127
Calcium (mg) 886±323 2,125±399 -1,2363 951±407 1,054±396 125
Fiber (grams) 21.7±7.9 35.9±6.6 14.23 22.6±8.1 27.1±8.5 4.9
Potassium (mg) 3,248±933 4,780±845 1,5323 3,413±1,031 3,873±1,114 494
Sodium (mg) 3,880±1,1244 2,625±578 -1445,6 4,344±1,5364 3,794±1,140 -3805
Magnesium (mg) 345±109 692±132 3473 363±113 391±108 32
Folate (ug) 309±116 749±131 4413 335±131 415±150 86

1All nutrient changes within treatment groups were significantly different from baseline, P<0.001, except for magnesium in the self-selected group women P<0.05, and self-selected group men, P<0.01; protein in prepared meal group women, P =0.48, and all men, P<0.01; carbohydrate in prepared meal group women and all men, P<0.05.
2x±SD
3Significantly different from the change in the self-selected diet P<0.05
4Significant difference in nutrient intake between groups, P<0.01
5Adjusted changes
6Significantly different from the adjusted change in the self-selected diet, P<0.05.

Changes in Endpoints Stratified by Sex and Treatment Group from Baseline to End of Treatment in Study Participants

                                

Prepared Meal Plan                                      

Change (N=163 W, 109 M)   

Self-Selected Diet                                                          Change (N=142 W, 128 M)

Variable: Women Sitting systolic BP (mmHg) -6.1±9.66 -4.5±9.62
Sitting diastolic BB (mmgHg) -3.4±5,42 -2.7±5.12
Cholesterol (mmol/L) -0.27±0.592 -0.22±0.522
Triacylglycerol (mmol/L) -0.07±1.34 -0.24±0.614
LDL (mmol/L) -.19±0.452 -0.12±0.433
HDL (mmol/L) -0.04±0.14 -0.03±0.134
VLDL (mmol/L) -0.03±00.61 -0.06±0.284
Insulin (mmol/L) -16.5±49.22 -18.7±91.84
HbA1c (percentage) -0.3±0.72 -0.2±0.62
Plasma Glucose (mmol/L) -0.6±1.92 -0.6±1.62
Weight (kg) -4.8±3.02,5 -2.8±2.82
Variable: Men Sitting systolic BP (mm/Hg) -7.0±8.52,6 -4.8±8.52
Sitting diastolic BB (mmg/Hg) -5.4±5.92,7 -3.2±5.12
Cholesterol (mmol/L) -0.39±0.572 -0.33±0.612
Triacylglycerol (mmol/L) -0.17±0.754 -0.21±0.824
LDL (mmol/L) -0.30±0.492 -0.21±0.462
HDL (mmol/L) -0.03±0.114 -0.02±0.10
VLDL (mmol/L) -0.09±0.38 -0.09±0.384
Insulin (mmol/L) -27.7±115.04 -16.7±67.2 4
HbA1c (percentage) -0.4±0.92 -0.5±0.92
Plasma glucose (mmol/L) -0.7±1.93 -0.9±2.42
Weight (kg) -4.5±3.62,5 -3.5±3.32

x±SD. HbA1c (glycated hemoglobin)
2-4Significant changes from baseline to the end of treatment were noted for all study endpoints except for triaclyglycerols and VLDL in women in the prepared meal plan group and HDL in men in the self-selected diet group:
2 P <0.0001
3P<0.001
4
P<0.05
5-7Significant changes from baseline for diet group:
5
P<0.0001
6P <0.05
7P<0.01.

Other Findings

  • Across all definitions of compliance, participants following the prepared meal plan were significantly more compliant with their diet prescriptions than were participants in the self-selected diet group
  • Energy compliance was achieved by 83% of prepared meal plan participants compared with 72% of the self-selected diet participants
  • As expected percentage compliance increased in both groups as the definitions for fat compliance became more liberal. At 20% of energy from fat, 78% of the self-selected diet participants achieved compliance; at 25% of energy from fat 93% of the prepared meal plan participants compared with 56% of the self-selected diet group achieved compliance. At 30% energy from fat, 95% of prepared meal participants compared with 78% of self-selected diet participants achieved compliance.
  • Participants following the prepared meal plan were better able to meet the NCEP/AHA Step 1 and 2 recommendations than was the self-selected diet group.

 

Author Conclusion:

In conclusion, independent of the type of dietary intervention, compliant participants had significantly reduced blood pressures, plasma lipids and body weights across all levels of dietary compliance criteria compared with their non-compliant counterparts. The results of this study underscore the necessity of a high degree of compliance to achieve optimal reductions in CVD risk factors by dietary means. Creating programs that will optimize dietary compliance is critically important to reducing morbidity and mortality due to diet-sensitive chronic diseases. Prepared meal plans provide a simple and effective modality for meeting the plethora of dietary guidelines recommended for prevention and treatment of chronic diseases, for improving dietary compliance and for reducing CVD risk.

Funding Source:
Industry:
Campbell's Soup Co.
Food Company:
Reviewer Comments:

Strengths of the study include, strong research design with statistical as well as clinical significance, use of a large sample size, comparable study groups, and discussion of study limitations which might effect study outcomes. A limitation of this study, however is that diet compliance was based largely on analysis of three-day food records which are not necessarily completed with 100% accuracy. For a variety of reasons, actual food intakes tend to be underreported which could contribute to false-positive results. Authors also neglected to mention whether blinding was used in any portion of this study which would eliminate introduction of bias.

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) No
  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.) No
  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? ???
  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.) No
  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? 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? 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