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MNT: Weight Management (2015)

Kesman RL, Ebbert JO, Harris KI, Schroeder DR. Portion control for the treatment of obesity in the primary care setting. BMC Res Notes. 2011 Sep 9; 4: 346. PubMed ID: 21906302
Study Design:
Randomized Controlled Trial
A - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:
To assess the effectiveness of a randomized intervention including a portion control plate and dietary counseling for weight loss among obese patients in a general medicine primary care practice.
Inclusion Criteria:
  • Must have signed a universal research authorization at the Mayo Clinic
  • Male and female patients were eligible for enrollment if:
    • They were between the ages of 18 years and 75 years
    • BMI of 30 or more and less than 40 (obesity classes II and III).
Exclusion Criteria:
  • Presence of active cancer
  • Participation in an organized weight loss program
  • Currently weight loss medications
  • History of bulimia or anorexia
  • Current treatment for psychiatric illness other than anxiety or depression
  • Surgery within the three months before enrollment or planned during the study period
  • Current or planned pregnancy
  • History of gastric bypass or planned gastric bypass.
Description of Study Protocol:


  • If the patient provided a signed a universal research authorization to the Mayo Clinic allowing for chart reviews, the patient's body mass index (BMI) was reviewed prior to their appointment with their primary care provider
  • If potentially eligible based on BMI, a letter was sent to the patient informing them of the study and asking them to discuss enrollment with their primary care provider at their upcoming appointment
  • Male and female patients were eligible for enrollment if they were men and women between the ages of 18 years and 75 years with a BMI of 30 or more and less than 40 (obesity classes II and III)
  • At the appointment, the patient was informed of the study and asked if they would like to participate.


Randomized pilot study intervention.

Blinding Used

Sealed enveloped were used, stratified by gender, to assign groups.


Two groups, followed for six months after randomization:

  • Portion control intervention:
    • A 60-minute appointment with a dietitian was scheduled
    • A baseline assessment of weight history, nutrition intake, exercise and non-exercise activity was conducted
    • A dietitian reviewed food choices, portion control, consistency and timing of meals, meal plans and appropriate use of snacks
    • Patients received specific written instructions on how to use a commercially available calibrated portion control plate and bowl:
      • The portion control plate was made of clear glass with black print dividing it into three sections (one one-half and two one-fourth sections). One-half of the plate was labeled "vegetables," one-fourth was labeled "fish, lean meat, chicken and nuts," and one-fourth was labeled "potatoes, pasta, rice, beans and whole grains."
      • The bowl was clear glass with black print designating "one-third cup," "one-half cup" and "one cup"
      • The patient was instructed to use the plate for their largest meal of the day and encouraged to use the plate or bowl for all meals.
  • Usual care: Patients were given two pamphlets ("Lifestyle Changes for Healthy Weight" and "Exercise: Getting Started and Staying With It")
  • At study completion, patients were provided with a survey to assess their satisfaction with the intervention.

Statistical Analysis

  • Analyses were performed using an intention-to-treat approach whereby subjects were analyzed according to randomized treatment
  • No covariate adjustment was included in the primary analysis
  • Descriptive statistics were used to summarize demographic data and other baseline characteristics, along with the results of the satisfaction survey
  • Weight change from baseline, three months and six months was expressed as a percentage of baseline weight
  • Separate a priori analysis for the three-month and six-month time points for the time-by-treatment interaction effect
  • Weight change was compared between groups using the two-sample T-test
  • Analyses were conducted excluding subjects with missing data (complete case analysis) and also using the last observation carried forward to impute values for subjects who discontinued study participation
  • The difference in weight change between group (plate minus control) was summarized using a point-estimate and corresponding 95% CI
  • Two-tailed P-values of 0.05 or less were considered statistically significant.
Data Collection Summary:

Timing of Measurements

Measurements were taken at baseline, three months and six months

Dependent Variables

Weight assessments: Using digital clinic scales with shoes off and clothes worn.

Independent Variables

Dietitian contact:

  • Portion control intervention group were contacted by phone or email (based on patient preference) at one, three and five months by the dietitian who briefly provided additional counseling and assistance
  • Usual care intervention group did not see a dietitian. They were just given pamphlets at their regular clinic visits.
Description of Actual Data Sample:

Initial N

N=65 patients (25 males, 40 females) were randomized:
  • Usual care group: N=32
  • Portion control group: N=33.

Attrition (final N)

N=42 patients
  • Usual care group: N=23
  • Portion control group: N=19.


  Usual Care Group N=32 Portion Control Group N=33
Age, years
     Mean±SD 53.6±10.7 55.4±9.4
     Range 32 to 75 31 to 74

Other Relevant Demographics

  Usual Care Group N=32 Portion Control Group N=33
     Male 12 (38) 13 (39)
     Female 20 (62) 20 (61)
Education, N (percent)
     High school graduate 7 (22) 8 (24)
     Some college 12 (38) 14 (42)
     Four-year college degree of more 13 (41) 11 (33)
Work status, N (percent)
     Full-time 19 (59) 22 (67)
     Part-time 2 (6) 2 (6)
     Unemployed 1 (3) 1 (3)
     Retired 10 (31) 8 (24)
Current tobacco use, N (percent)
     No 30 (94) 32 (97)
     Yes 2 (6) 1 (3)
Diabetes, N (percent)
     No 25 (78) 25 (76)
     Yes 7 (22) 8 (24)
Current exercise, N (percent)
     None 4 (12) 4 (12)
     One to 90 minutes per week 8 (25) 13 (39)
     91 to 150 minutes per week 16 (50) 9 (27)
     More than 150 minutes per week 4 (12) 7 (21)


  Usual Care Group N=32 Portion Control Group N=33
Weight, kg
     Mean±SD 98.8±12.5 97.6±12.8
     Range 75.2 to 127.2 74.7 to 129.3


Mayo Clinic; Rochester, MN.

Summary of Results:

Key Findings

  Usual Care (N=32) Portion Control (N=33) Difference in Means (Plate-control)
  N Mean±SD (Min, Max) N Mean±SD (Minimum, Maximum) Estimate (95% CI) P-value
Three Months
Change from baseline (kg)
     Complete case 24 -0.6±2.2 (-6.4, +2.3) 23 -2.2±3.6 (-11.6, +4.2) -1.6 (-3.3, +0.1) 0.071
     Last value carried forward 32 -0.4±1.9 (-6.4, +2.3) 33 -1.5±3.1 (-11.6, +4.2) -1.1 (-2.4, +0.2) 0.099
Percent change from baseline
     Complete case 24 -0.5±2.2 (-5.2, +2.3) 23 -2.4±3.7 (-11.4, +3.9) -1.8 (-3.6, +0.7) 0.041
     Last value carried forward 32 -0.4±1.9 (-5.2, +2.3) 33 -1.7±3.3 (-11.4, +3.9) -1.3 (-2.6, +0.1) 0.062
Six Months
Change from baseline (kg)
     Complete case 23 -0.9±4.2 (-15.7, +3.9) 19 -1.9±3.7 (-10.0, +6.1) -1.0 (-3.5, +1.5) 0.414
     Last value carried forward 32 -0.5±3.6 (-15.7, +3.9) 33 -1.0±3.0 (-10.0, +6.1) -0.5 (-2.2, +1.1) 0.528
Percent change from baseline
     Complete case 23 -0.7±3.7 (-12.3, +3.7) 19 -2.1±3.8 (-9.8, +5.6) -1.4 (-3.7, +0.9) 0.232
     Last observation carried forward 32 -0.4±3.2 (-12.3, +3.7) 33 -1.2±3.1 (-9.8, +5.6) -0.8 (-2.3, +0.8) 0.311


Other Findings

  • Among those who completed the study, subjects in the portion control intervention had a greater percentage weight change from baseline compared to usual care (-2.4±3.7% vs. -0.5±2.2%; P=0.041) at three months
  • A trend toward increased weight loss with the portion control intervention was observed using the Last Observation Carried Forward (LOCF) analysis (-1.7±3.3 vs. -0.4±1.9; P=0.062) at three months
  • Non-significant trends toward increased weight loss with the portion control intervention were observed at six months
  • Among the participants who completed the intervention group (N=19), 47% perceived that the overall portion control intervention was helpful
  • A total of 68% endorsed that the counseling at the dietitian visit was helpful
  • A total of 79% would recommend the portion plate to family or friends
  • A total of 32% reported that they used the plate for one meal per day, while 37% and 26% said that they used the plate for two or three meals per day
  • A total of 42% of patients said they would continue to use the portion plate after the study.
Author Conclusion:
  • Weight loss among obese patients receiving a portion control intervention including dietary counseling and a portion control plate in a primary care general medicine practice
  • Larger studies are needed to assess the utility of portion control tools in primary care and corroborate the findings of this small clinical pilot.
Funding Source:
University/Hospital: Mayo Clinic
Reviewer Comments:
In the statistical methods section, the authors determined that a sample size of 80 patients would provide statistical power (two-tailed, alpha equals 0.05) of 83% to detect a difference between groups. However, because there was a shortage of portion control bowls, they decided to discontinue enrollment after randomizing 65 subjects. This means that it would provide a statistical power (two-tailed, alpha equal 0.05) of 75% to detect a difference in weight change of 2% between groups.

There was a question as to why they didn't just select a different company to get portion control bowls from.
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? ???
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? ???
  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? 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? ???
  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? ???
  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? No
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes