Final Research Report

This project's final research report is temporarily unavailable and will be reposted soon.

More to Explore...


Partnering to Help People with Obesity Better Understand Their Surgical Options
Read more about how this study used vast data from PCORnet®, The National Patient-Centered Clinical Research Network, to study outcomes among the three most common weight-loss surgeries.

Bariatric (Weight-Loss) Surgery to Treat Type 2 Diabetes
"Diabetes Discoveries & Practice Blog," National Institute of Diabetes and Digestive and Kidney Diseases
In a Q&A, Principal Investigator David Arterburn describes this study's findings and discusses bariatric surgery guidelines for patients with type 2 diabetes.

Related PCORI Dissemination and Implementation Project

Evidence for Decisions

Comparing Two Types of Weight Loss Surgery
Bariatric surgery can help people with obesity lose weight, among other potential benefits. But surgery can also cause harm, and outcomes may vary across different procedures. This study compared the benefits and harms of the two most common types of bariatric surgery. The findings can help clinicians and patients work together to make informed decisions regarding patient care.

Journal Citations

Article Highlights: The PCORnet® Bariatric Study, which is using data from PCORnet, The National Patient-Centered Clinical Research Network, to study outcomes among patients who undergo common weight-loss surgeries, has published several papers in prominent medical journals. The most recent clinical findings, published in JAMA Surgery, are on diabetes remission outcomes among patients who underwent gastric bypass and gastric sleeve surgeries. Another article, also published in JAMA Surgery, details the five-year outcomes of patients who underwent either gastric bypass or adjustable banding, finding that gastric bypass patients were significantly more likely than gastric sleeve patients to end up back in the hospital in the years following surgery.

Peer-Review Summary

Peer review of PCORI-funded research helps make sure the report presents complete, balanced, and useful information about the research. It also assesses how the project addressed PCORI’s Methodology Standards. During peer review, experts read a draft report of the research and provide comments about the report. These experts may include a scientist focused on the research topic, a specialist in research methods, a patient or caregiver, and a healthcare professional. These reviewers cannot have conflicts of interest with the study.

The peer reviewers point out where the draft report may need revision. For example, they may suggest ways to improve descriptions of the conduct of the study or to clarify the connection between results and conclusions. Sometimes, awardees revise their draft reports twice or more to address all of the reviewers’ comments. 

Peer reviewers commented and the researchers made changes or provided responses. Those comments and responses included the following:

  • The reviewers asked why the researchers did not perform propensity score analyses on some specific parts of the study, such as safety outcomes, to account for any differences between groups in this observational study. The researchers explained that they found the propensity score adjustments did not change results enough to warrant accepting certain assumptions and checking propensity distributions.  In addition, because the hypotheses in these studies were associative instead of causal, the reviewers felt that the covariate adjustment was sufficient without a propensity score adjustment.
  • The reviewers asked whether the researchers specified subgroup analyses in advance and whether they were driven by hypotheses. The researchers responded that they specified all subgroup analyses in advance but that they considered the analyses exploratory rather than driven by hypotheses.
  • The reviewers asked why in the qualitative study, patient feedback was sought in focus groups rather than in individual interviews. Since obesity and bariatric surgery can be socially sensitive topics, the reviewers noted that having to answer questions in a group setting may have affected responses. The researchers said funding constraints did not allow for individual interviews, particularly since they wanted to maximize sample size and representation of patients from different parts of the country. They acknowledged that using focus groups was a limitation of the study.
  • The reviewers asked why the frequency of obesity-related cancers, including colorectal cancer, was not analyzed as an outcome. The researchers explained that they excluded patients with certain types of cancers, especially gastrointestinal (GI) cancers, because some patients with GI cancer will undergo a procedure for the cancer that is coded the same as bariatric surgery in electronic health records. 

Conflict of Interest Disclosures

Project Information

David Arterburn, MD, MPH
Kaiser Permanente Washington Health Research Institute^
Comparing the Benefits and Harms of Three Types of Weight Loss Surgery -- The PCORnet® Bariatric Study

Key Dates

August 2015
July 2022

Study Registration Information

^Kaiser Permanente acquired Group Health Cooperative in February 2017.


Has Results
Health Conditions Health Conditions These are the broad terms we use to categorize our funded research studies; specific diseases or conditions are included within the appropriate larger category. Note: not all of our funded projects focus on a single disease or condition; some touch on multiple diseases or conditions, research methods, or broader health system interventions. Such projects won’t be listed by a primary disease/condition and so won’t appear if you use this filter tool to find them. View Glossary
Populations Populations PCORI is interested in research that seeks to better understand how different clinical and health system options work for different people. These populations are frequently studied in our portfolio or identified as being of interest by our stakeholders. View Glossary
Intervention Strategy Intervention Strategies PCORI funds comparative clinical effectiveness research (CER) studies that compare two or more options or approaches to health care, or that compare different ways of delivering or receiving care. View Glossary
State State The state where the project originates, or where the primary institution or organization is located. View Glossary
Last updated: July 8, 2022