MNT: RDN in Medical Team (2015)

Win AZ Ceresa C, Schafer AL, Mak, P, Stewart L. Importance of nutrition visits after gastric bypass surgery for American veterans, San Francisco, 2004–2010. Prev Chronic Dis. 2014; 11 :E226. PubMed ID: 25539130
Study Design:
Retrospective Cohort Study
B - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:
To explore the relationship between the number of nutrition visits a patient made and change in body mass index (BMI) after gastric bypass surgery for the veteran population.
Inclusion Criteria:
Data collected from de-identified patient records of those who underwent roux-en-y gastric bypass (RYGB) at San Francisco VA facility between June 2004 and July 2010.
Exclusion Criteria:
Did not undergo RYGB at San Francisco VA facility during defined timeframe of June 2004 to July 2010.
Description of Study Protocol:


Recruited from San Francisco VA.


The project was reviewed and approved by the San Francisco Veterans Administration Medical Center Institutional Review Board. Before analysis, patient records and information were de-identified to ensure anonymity. Data from patients who underwent RYBG at the facility via computerized patient record system. Date of surgery, age, sex race, height, BMI, number of nutrition encounters during the two years after surgery and weight before and two years after surgery were recorded.


No intervention. Relationship between the number of nutrition visits a patient made and change in BMI after gastric bypass surgery was explored.

Statistical Analysis

  • Spearman's correlation used to determine the association between number of nutrition visits and BMI change
  • Multi-variate linear regression used to determine effects of nutrition visits, sex, race and age on BMI change
  • P<0.05 considered significant.
Data Collection Summary:

Timing of Measurements

Collected from patients' records:
  • Date of surgery 
  • Age
  • Sex
  • Race
  • Height
  • BMI
  • Number of nutrition encounters during two years after surgery
  • Weight before and two years after surgery
  • BMI calculated as weight divided by height
  • Change in BMI calculated by subtracting pre-surgery BMI from two year post-surgery BMI.

Dependent Variables

Change in BMI.

Independent Variables

Number of nutrition encounters for two years after surgery.

Control Variables

  • Date of surgery 
  • Age
  • Sex
  • Race.
Description of Actual Data Sample:
  • Initial N: N=79 patients (82% male, 18% female)
  • Attrition (final N): N=79 patients
  • Age: 51.35±8.73 years
  • Ethnicity: White 70%, Black 19%, Hispanic 11%
  • Location: San Francisco, California.


Summary of Results:

Key Findings

  • Mean number of nutrition encounters during the two years post-surgery was 6.44±5.36 visits, range one to 29 visits
  • Average BMI change was decrease of 14.66±6.26, range 1.3 to 38.1 at two years post-surgery
  • Significant relationship between the number of post-surgery nutrition encounters and the change in BMI two years after surgery (Spearman's rho=0.21; P=0.017)
  • After adjusting for age, sex and race, there was an association between post-surgery nutrition visits and BMI change (beta=0.255; 95% CI: 0.015 to 0.581; P=0.039).
Multivariate Linear Regression Analysis of Factors Affecting Post-surgery Weight Loss
Variable Beta P-value 95% Confidence Interval
Post-surgery nutrition visits 0.255 0.04 0.015 to 0.581
Age -0.091 0.45 -0.238 to 0.107
Sex -0.004 0.96 -3.181 to 3.342
Race 0.006 0.97 -1.74 to 1.683
Author Conclusion:
Veterans attending more nutrition visits following surgery experienced greater declines in BMI in the two years after surgery.
Funding Source:
Government: Department of Veterans Affairs
Reviewer Comments:
Study limitations include:
  • Retrospective study
  • Patients were mostly white, male and over the age of 50 years
  • Small sample size.
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) N/A
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? N/A
  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? Yes
  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? Yes
  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.) N/A
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? Yes
  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? N/A
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? 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
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? Yes
  6.6. Were extra or unplanned treatments described? 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
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