PDM: Prediabetes (2013)


de la Cruz-Munoz N, Messiah SE, Arheart KL, Lopez-Mitnik G, Lipshultz SE, Livingstone A. Bariatric surgery significantly decreases the prevalence of type 2 diabetes mellitus and pre-diabetes among morbidly obese multiethnic adults: long-term results. J Am Coll Surg. 2011; 212(4): 505-511.

PubMed ID: 21463779
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 examine pre- vs. post-surgery mean weight, estimated weight loss (EWL), body mass index (BMI), fasting plasma glucose (FPG) and hemoglobin A1C values to examine the improvement in glucose metabolism and weight.

Inclusion Criteria:

Adults who met the criteria for the NIH bariatric surgery (BMI higher than 35kg/m2 with one or more existing co-morbidity or BMI 40kg/m2) and underwent gastric bypass/banding surgery in a single surgeon's practice from 2002 to 2010.

Exclusion Criteria:

Not described.

Description of Study Protocol:


Data for this study was obtained from a retrospective medical chart analysis of adults who met the NIH criteria for bariatric surgery and underwent gastric bypass or banding surgery in a single surgeon's practice from 2002 to 2010.


Retrospective analysis of 1,603 adults who underwent bariatric surgery from 2002 to 2010.

Blinding Used

Implied with measurements.

Statistical Analysis

  • Analysis of variance was used to test for baseline differences in all demographic variables:
    • Weight
    • BMI
    • EWL
    • HbA1c
    • FPG
  • For assessment of longitudinal change in weight and BMI, separate repeated-measures mixed linear models were fit using the MIXED procedure in SAS (version 9.2)
  • A variance-covariance matrix was selected for each model to account for the correlation of within-patient repeated observations
  • Within-group contrasts of mean values of weight, BMI, EWL, FPG and HbA1c for each time period were conducted to test for mean differences by group via least square means analysis
  • Statistical tests resulting in a probability of 0.05 or less were considered significant.
Data Collection Summary:

Timing of Measurements

Subjects followed from 2002 to 2010.

Dependent Variables

  • Pre- and post-surgery height and weight were measured during routine clinical visits by practice nursing staff

  • Weight was measured to the nearest 0.1kg using a digital scale with the participants wearing light clothing and no shoes
  • Height was measured to the nearest 0.5cm using an Accustat Genentech stadiometer
  • The BMI was calculated as body weight in kg divided by height in m2
  • Weight loss was expressed as EWL in kg
  • FPG was measured by a modified hexokinase enzymatic method of 100 to 125mg per dL
  • The HbA1c was measured by immunoassay and was included as a component of the standard pre- and post-surgery laboratory measurements
  • Blood work (complete blood count, vitamin B12, calcium, parathyroid hormone, and uric acid levels and iron studies was performed every six months for the first two years and then yearly thereafter).

Independent Variables

Adults who met the NIH criteria for bariatric surgery and underwent gastric bypass or banding surgery in a single surgeon's practice.

Description of Actual Data Sample:
  • Initial N: 1,603 men and women (77% female)
  • Attrition (final N): 1,603 men and women
  • Age: Mean age at surgery 45.1 years SD 11.6 years
  • Ethnicity: 66% Hispanic
  • Other relevant demographics: 377 subjects had T2DM determined by previous diagnosis and or medication usage, 107 had FPG 126mg per dL or more, but were not on medication and were labeled as undiagnosed T2DM, 276 had pre-diabetes (FPG=100 to 125mg per dL) and 843 had normal FPG pre-surgery
  • Location: Miami, Florida.
Summary of Results:

Key Findings

  • Patients with pre-diabetes saw the most dramatic weight loss in weight (47kg), followed closely by undiagnosed T2DM (46.2kg), normal IFG (43.14kg) and T2DM (41.39) at three years post-surgery
  • For all groups, the most weight was lost in the first 12 months following surgery. All four groups had very similar BMI measures (range of 2.7mg per dL) and were within 6.96 EWL% of each other at three years post-surgery
  • Dramatic decreases in FPG and HbA1c were seen for all groups. By one year post-surgery, all groups were within the normal FPG range according to ADA criteria, and this was maintained through three years post-surgery
  • Undiagnosed T2DM patients saw the most dramatic decrease (70.2mg per dL) (43%) followed by diagnosed T2DM patients 49.09mg per dL (33%)
  • Conversely, diagnosed T2DM patients showed a slightly greater loss in HbA1c (2.3%) vs. undiagnosed T2DM (2.13%)
  • No significant decrease in BMI was seen for any group from 24 to 36 months post-surgery
  • All four groups showed a significant decrease in FPG in the first six months post-surgery (P<0.0001 for all)
  • The IFG continued to significantly decrease from six to 12 months among patients with T2DM (P=0.05) and those with undiagnosed T2DM (P=0.001) whereas, those with a normal initial FPG saw a significant rise in FPG (P<0.0001)
  • Patients with diagnosed and undiagnosed T2DM and those with pre-diabetes all showed a significant decrease in HbA1c in the first six months post-surgery (P<0.0001 for all)
  • After three years, patients with pre-diabetes had significant reductions in fasting plasma glucose (from 105.49±0.52 to 84.63±1.52mg per dL, P<0.0001) and hemoglobin A1C (from 6.10±0.09% to 5.60±0.07%, P<0.0001).


Author Conclusion:

Results from this study show that bariatric surgery results in significant weight loss and improvement in FPG and HbA1c levels as far as three years post-surgery among ethnically diverse adults. Bariatric surgery has the potential to be an effective treatment option for weight loss and chronic disease risk improvements in this demographic.

Funding Source:
University/Hospital: Department of Surgery Pediatrics, Division of Pediatric Clinical Research
Reviewer Comments:

The authors noted that the main study limitation was not having medication information available post-surgery for the T2DM group, making it impossible to attribute the normal IFG and HbA1c levels to weight loss or bariatric surgery alone. However, the patients with undiagnosed T2DM were known to be on no T2DM medications pre and post-surgery and showed maintenance of normal levels of both parameters as far as three years post-surgery.

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? N/A
  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.) N/A
  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? 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)? 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? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes