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SSPSM: Weight Loss (2014)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
To examine the efficacy of a commercially available, portion-controlled diet (PCD) on body weight and HbA1c over six months in obese patients with type 2 diabetes.
Inclusion Criteria:
  • BMI of 25kg/m2 to 50kg/m2
  • Age of 21 to 75 years
  • A screening HbA1c of 6.5% or more and less than 12.0%
  • All classes of diabetes medications was permitted (including insulin), provided they had been prescribed at stable doses for three or more months (or six or more months in the case of incretin mimetics and pramlintide), as was the case for medications for other conditions (e.g., hypertension, dyslipidemia).
Exclusion Criteria:
  • Significant cardiovascular, pulmonary, hepatic, renal or gastrointestinal disease
  • Uncontrolled hypertension (160/100mm Hg or more)
  • History of alcohol or drug abuse
  • Significant psychiatric conditions thought to impair the candidate’s safe or successful study participation
  • Use of psychiatric medications (except for selective serotonin reuptake inhibitors)
  • Pregnancy or lactation
  • Bariatric surgery
  • Use of weight-loss–inducing medications or supplements in the prior three months
  • Weight loss 5kg or more in the prior six months.
Description of Study Protocol:

Recruitment

Recruited and treated at two medical centers in Philadelphia.

Design

Randomized controlled trial.

Blinding Used

Implied with measurements.

Intervention
 

  • Participants were randomized to one of two treatment conditions: Lifestyle intervention with portion-controlled diet (PCD) program or a DSME program
  • Participants who received the PCD were instructed to supplement the pre-packaged foods (which typically provided three entrees and one snack daily) with conventional foods (e.g., fruits, vegetables, dairy items and lean protein), in accordance with the PCD program. Women’s and men’s meal plans provided 1,250kcal and 1,550kcal per day, respectively, with 55% of total energy from the packaged foods and 45% from supplemental grocery items. The plans were structured to provide 50% to 55% of energy from carbohydrate, 20% to 25% from fat and 20% to 25% from protein, and to contain 2,300mg per day of sodium.
  • DSME was intended to model structured diabetes self-management training programs provided by certified diabetes educators in medical settings. Participants were instructed to consume a balanced deficit diet consistent with recommendations of the Food Guide Pyramid and the American Diabetes Association. The suggested macronutrient content was 15% to 25% of calories from protein, 30% from fat (7% from saturated fat) and the remainder from carbohydrate, with 30g per day of fiber. Meal plans were provided to help participants meet their nutrition and calorie goals.

Statistical Analysis

Differences between the groups on baseline characteristics were assessed using independent samples T-tests for continuous variables and chi-square tests for categorical variables. The primary outcome was the change in body weight (kg) at month six, as determined using a linear mixed-effects model with time, treatment and a time by treatment interaction included as explanatory variables. Categorical secondary outcomes (e.g., changes in medication regimen intensity, achievement of clinically meaningful targets for weight loss and HbA1c) were analyzed using chi-square tests or Fisher’s Exact Test. Alpha was set at P<0.05 for the comparison of the two treatment conditions on the primary outcome (weight change), as well as on all secondary outcomes.

Data Collection Summary:

Timing of Measurements

Main outcomes (weight) were assessed at baseline, three and six months.

Dependent Variables

  • Weight measured with calibrated electronic scale, light clothing without shoes
  • Height measured using wall-mounted stadiometer.

Independent Variables

PCD vs. DSME program for weight loss.

Control Variables

  • Length of intervention and timing of measurements: Participants in both treatment conditions attended group sessions (at weeks zero, one, two, four, eight, 12, 16, 20 and 24) that lasted 90 minutes; included eight to 12 persons and were led by experienced practitioners (that is, lifestyle interventionists or certified diabetes educators, as appropriate).
  • Participants in both treatment conditions were instructed to consume 1,250kcal per day (women) or 1,550kcal per day (men) and were provided a calorie-counting guide to facilitate this goal.
  • Participants were instructed to gradually increase their walking (or other aerobic activity) to 200 or more minutes per week.
Description of Actual Data Sample:
  • Initial N: 50 PCD (42% male, 58% female) and 50 DSME (40% male, 60% female)
  • Attrition (final N): 49 PCD and 50 DSME
  • Age: 55.6±10.6 years
  • Ethnicity: 36% White, 59% African-American, 3% Asian, 2% Hispanic/Latino, 2% other
  • Other relevant demographics: BMI 35.8±5.3kg/m2
  • Anthropometrics: Groups were similar at baseline
  • Location: Philadelphia, PA, United States.
Summary of Results:

Key Findings

Weight Loss

 

Variables PCD
(N=50 BL, 49 at Six Months)		 Control Group: DSME
(N=50 BL, 50 at Six Months)		 Statistical Significance of Group Difference
Body weight (kg)
  Baseline 101.8±16.7 104.0±20.1 <0.0001
  Six months 93.9±14.7 101.8±19.4
  Adjusted change -7.3 (-8.8 to -5.8) 2.2 (-3.7 to -0.7)
BMI (kg/m2)
  Baseline 35.3±4.6 36.2±5.8 <0.0001
  Six months 32.6±4.2 35.5±5.8
  Adjusted change -2.5 (-3.0 to -2.0) -0.7 (-1.2 to -0.2)

 

  • While both groups produced significant improvements in weight and HbA1c after six months of treatment, PCD participants lost 7.3kg (95% CI: 5.8kg to 8.8kg), compared with 2.2kg (95% CI: 0.7kg to 3.7kg) in the DSME group (P<0.0001)
  • These losses corresponded to reductions in initial weight of 7.8% and 2.1% for PCD and DSME, respectively
  • Directionally similar differences were observed between the groups at month three (5.6kg vs. 1.8kg)
  • A significantly greater percentage of participants in the PCD than DSME groups lost 5% or more of initial weight at month six (54.0% vs. 14.0%, P<0.0001), as well as 10% or more (26.0% vs. 6.0%, P<0.0001) (Note: The percentage of participants who lost 5% or more includes those who lost 10% or more)
  • HbA1c declined by 0.7% (95% CI: 0.4% to 1.0%) in the PCD group, compared with 0.4% (95% CI: 0.1% to 0.7%) in DSME (P<0.026)
  • Across both groups, larger weight losses were associated with greater reductions in HbA1c (R=0.52, P<0.0001).

 

Author Conclusion:
A lifestyle intervention that included a PCD induced significantly greater weight loss in six months than did a comprehensive diabetes self-management and education program that provided instruction in weight management and control of diabetes complications.
Funding Source:
Industry:
Nutrisystem, Inc; LifeScan, Inc
Food Company:
Other:
In-Kind support reported by Industry: Yes
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
  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) 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? 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? 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? 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.) 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? 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? 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