NC: Behavior Change Strategies (2007-2008)

Study Design:
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Quality Rating:
Research Purpose:
To test the hypothesis that liquid meal replacements given once or twice daily in addition to a low-fat diet can provide sustained weight reduction and that a 5 - 10% loss of body weight can cause a sustained improvement in disease-related biomarkers.
Inclusion Criteria:
Patients were men and women over 18 years of age, with BMI 25 - 40 and who indicated willingness to participate in the study.
Exclusion Criteria:
Individuals with a history or presence of significant disease, endocrine disorder, psychiatric disease, alcohol or drug abuse, or abnormal laboratory tests of clinical significance were excluded.  In addition, women were excluded if they were lactating, pregnant, or wished to become pregnant. 
Description of Study Protocol:


Patients were referred by physicians because of past dissatisfaction with a standard energy-restricted diet plan for >3 months.


Prospective, randomized, two-arm parallel intervention for 12 weeks followed by a prospective, single-arm 4-year trial. 

Blinding used (if applicable)

Not blinded.

Intervention (if applicable)

Randomly assigned by a computer-generated identification number to 1 of 2 diets:  Group A received a 1200-1500 kcal control diet (19-21% kcals from protein, 48-54% kcals from carbohydrate, 25-34% kcals from fat), Group B received an isoenergetic diet, including 2 meal and snack replacements (Slim-Fast vitamin and mineral fortified shakes, soups and bars:  200-220 kcals, 14-17 g protein, 27-33.5 g carbohydrate, 5-6.6 g fat, 4.5-6.5 g fiber) and 1 meal high in fruits and vegetables (600-900 kcal, 30-45 g protein).  After 3 months, patients were prescribed the same caloric reduction and used once-daily replacements for the next 4 years.  Meal replacement products provided for free.

Statistical Analysis

Patients were analyzed according to their original assignment.  Comparisons of values between the 2 groups were calculated by using a 2 sample t test.  Values are given as mean +/- SD unless stated otherwise.  For phase I, a linear regression model was fit for percentage weight change and absolute body weight with sex and group as covariates.  Generalized estimating equations were used to analyze phase II of the study.  An unstructured, working correlation matrix was assumed for the GEE algorithm for all outcomes except percentage weight change, for which a compound symmetric structure was assumed.  GEEs are a method of analyzing longitudinal data that do not rely on distributional assumptions.  Furthermore, they give robust estimates of parameters and their SEs.  For each outcome of interest, a GEE model was fit with group, time and baseline outcome as main effects and all interactions between group and time.  All outcomes were measured at 3, 9, 15, 27 and 51 months.

Data Collection Summary:

Timing of Measurements

Patients received monthly instruction in behavior modification from the dietitian. Body weight and blood pressure checked monthly.  Biomarkers of disease risk measured at baseline and after 3, 9, 15, 27 and 51 months.

Dependent Variables

  • Body weight measured to the nearest 0.1 kg using the same precision scale, patients dressed only in underwear
  • Blood pressure measured to the nearest 5 mm Hg on the upper right arm using a mercury column manometer, patient in a supine position and rested for at least 10 minutes
  • Blood samples taken at least 10 hours after previous meal and biochemical measurements performed by standard methods

Independent Variables

  • Dietary intervention:  assigned to group A or B.  Food exchange lists and food diaries were used to equalize energy and protein intake between groups.  Daily food diaries were maintained for 7 consecutive days during the 2-week period before each visit.

Control Variables


Description of Actual Data Sample:

Initial N: 100 subjects, 21 male, 79 female

Attrition (final N):  100 subjects after 12 weeks, 75 subjects after 4 years, 60 female, 15 male.  At the end of the second year, 63 completed the study.  By month 37, 58 patients continued.  32 of the 42 dropouts were located and 22 reentered the study between months 37 and 41.

Age:  Mean age Group A:  46.5 +/- 11.6 years, Mean age Group B:  44.8 +/- 9.7 years 

Ethnicity: Not mentioned.

Other relevant demographics:  Patients encouraged to maintain usual level of activity.  Average BMI:  33.6 +/- 3.6 

Anthropometrics Baseline characteristics showed no significant differences between the 2 groups in sex distribution, age, body weight, or BMI.

Location:  University of Ulm Obesity Center, Germany 


Summary of Results:


Baseline 3 months

27 months

Energy (kcal/d) - A 1797 +/- 203 1663 +/- 86 1606 +/- 84, p <0.05
Energy (kcal/d) - B 1814 +/- 84 1375 +/- 43, p < 0.05 1577 +/- 69, p < 0.05
Energy from fat (kcal/d) - A 676 +/- 79 547 +/- 82, p < 0.05 476 +/- 52, p < 0.05
Energy from fat (kcal/d) - B 655 +/- 55 340 +/- 43, p < 0.05 433 +/- 62, p < 0.05
Cholesterol (mg/d) - A

422 +/- 57

244 +/- 30, p < 0.05

188 +/- 30, p < 0.05

Cholesterol (mg/d) - B

378 +/- 43

154 +/- 14, p < 0.05

176 +/- 19, p < 0.05

Other Findings

In both groups, energy intake had decreased after 3 months, and in Group B, the decrease was significant (p < 0.05).  The difference in the energy intake between groups was also significant (p < 0.001).

After 27 months, the reported intake in Group A was reduced by 10.4% compared with baseline (p < 0.05).  In Group B, the reported energy intake after 27 months had increased but remained 13.1% below energy intake reported at baseline (p < 0.05).

After 3 months, cholesterol intake was reduced by 42.2% in group A (p <0.05) and by 59.3% in group B (p < 0.05).  After 27 months, the reported cholesterol intake was below 200 mg/dl.

During 3-month weight loss period, body weight was reduced by 1.5 +/- 0.4% for group A (mean 1.3 +/- 0.4 kg, p < 0.001 compared with baseline) and 7.8 +/- 0.5% for group B (mean 7.1 +/- 0.5 kg, p < 0.001 compared with baseline). 

After 4 years, total mean weight loss was 3.3 +/- 0.8% for group A and 8.4 +/- 0.8% for group B.

Both groups of patients showed significant improvement in glucose, insulin, triacylglycerol and systolic blood pressure.

Cholesterol concentrations were reduced in patients with high initial cholesterol levels and maintenance of a 7% weight loss. 

Author Conclusion:
This prospective dietary intervention study of obese subjects demonstrates that the diet plan with liquid meal replacements resulted in greater weight loss than the self-selected diet composed of regular food.  Providing a structured meal plan with liquid meal replacements is an effective treatment for obese subjects.  Long-term maintenance of weight loss with meal replacements improves biomarkers of disease risk.
Funding Source:
University/Hospital: University of Ulm (Germany)
Reviewer Comments:
0% dropout rate after 12 weeks, but dropout more signficant over time.  Exercise not monitored.  Supported by Slim Fast Foods Co.
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? 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? ???
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? ???
  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%.) No
  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? ???
  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? ???
  6.6. Were extra or unplanned treatments described? ???
  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? ???
  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? ???
  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? No
  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)? N/A
  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? ???
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? ???