A PCORI-funded study documented differences in the benefits and harms of two common types of bariatric surgery. The findings can help clinicians and patients work together to make informed decisions regarding patient care.1,2


A female medical professional seated next to a female patient as she listens to her lungs with a stethoscope.

Obesity is associated with a range of comorbidities including type 2 diabetes mellitus (T2DM). Bariatric surgery may be a viable treatment for patients with a body mass index (BMI) of 35 or greater who are unable to lose weight through diet and exercise alone. However, outcomes vary across procedures.

A PCORI-funded study compared the benefits and harms of the two most common types of weight loss surgery: Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG). The study included a third type of surgery, adjustable gastric banding. Because this surgery is no longer commonly used, the results are not included in this Evidence Update.


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A PCORI-funded study found that both procedures resulted in weight loss and remission of T2DM for the majority of patients. Overall, RYGB had better total weight loss results and a more significant impact on increasing T2DM remission and improving glycemic control compared with SG. However, RYGB was also associated with a higher rate of adverse outcomes such as additional abdominal surgeries and rehospitalization.

Comparing the Benefits

Weight Loss

Patients in the RYGB cohort saw a higher percentage of total weight loss over a five-year period following surgery than patients in the SG cohort.3 Patients in both cohorts experienced some level of weight gain after their initial weight loss.

Average Percent of Total Weight Loss Following Surgery (Compared with Pre-Surgery Weight)
Average weight lost in first year 31% 25%
Average weight lost at five years 26% 19%

Type 2 Diabetes Outcomes

RYGB and SG resulted in clinically comparable T2DM remission rates throughout the five-year period following surgery.4 Remission is defined as HbA1c under 6.5% after six months without a diabetes medication prescription. Most T2DM remission occurred within two years of surgery. The risk of relapse was 25% lower for patients who had RYGB compared with patients who had SG.

Percent of Cohort Experiencing Type 2 Diabetes Remission and Relapse
T2DM remission during five-year period post-surgery 86% 84%
T2DM relapse during five-year period post-surgery 33% 42%


Glycemic Control

Patients with diabetes who had RYBG showed a 0.80 percentage point drop in hemoglobin A1c (HbA1c) over five years of follow-up. HbA1c was reduced 0.45 percentage points more for patients who had RYGB than for patients who had SG when compared to baseline measurements.

Comparing the Harms

Additional Surgery. Fewer patients in the SG cohort needed to have further abdominal intervention within five years compared with patients in the RYGB cohort. Further surgical interventions included any additional bariatric procedure or other procedure related to device removals, gastric revisions, abdominal or incisional hernia repair, laparoscopy or laparotomy, or percutaneous endoscopic gastrostomy tube placements.5

Hospitalization. Patients in the SG cohort were less likely to require hospitalization within five years than patients in the RYGB cohort. Hospitalization was defined as any inpatient hospitalization following bariatric surgery that was not associated with a delivery or other obstetric procedure.

Cumulative Probability of Adult Bariatric Surgery Recipients Experiencing Harms Post-Surgery
Needing further abdominal intervention or surgery 12% 9%
Requiring hospitalization within five years 38% 33%

Mortality. Overall mortality rates were similar between RYGB and SG, with both at less than 1% at five years.

Providing Comprehensive Patient Support

Qualitative findings from this study found that patients faced mental, social, and physical challenges both pre- and post-surgery.6 For example, some patients reported experiencing negative reactions from friends, family, and co-workers who discredit individuals who lose weight through bariatric procedures. These findings suggest that both primary care providers and bariatric specialists may want to consider a comprehensive approach to supporting patients before and after bariatric surgery that includes:

Helping patients develop realistic expectations for physical and psychological outcomes and the need for lifelong follow-up care from a surgeon or bariatrician

Providing strategies for coping with emotional and interpersonal challenges, for example through psychological therapy or participation in online support groups

Educating patients on making and maintaining changes in eating behavior and exercise

Preventing adverse outcomes like cross-addictions and large weight gain post-surgery

What Do the Guidelines Say about Bariatric Procedures?

Professional organizations do not recommend a specific type of bariatric surgery. They recommend that doctors and patients decide about bariatric surgery together based on factors such as the patient’s health, weight loss goals, preferences, and safety.7

Talking with Patients about Bariatric Surgery

A patient-friendly version of this update is available here to help bariatric care teams talk with patients and caregivers about the benefits harms to consider when choosing a treatment. Topics for discussion include:

Patients’ and caregivers’ expectations for bariatric surgery

Surgery outcomes that are most important to the patient

Patient risk factors that can inform the choice of procedure

Lifestyle changes needed before and after surgery, including diet and exercise

Post-operative experiences

The importance of having an adequate support system

About the Study

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The research team used patient health record data from PCORnet®, the National Patient-Centered Clinical Research Network, to examine how bariatric surgery affected (1) weight loss in 46,510 adults; (2) outcomes related to diabetes in 10,019 adults with type 2 diabetes; and (3) the need for more surgery in 34,714 adults.

The data were from 41 health systems across the country for patients who had a BMI of at least 35 and had surgery between 2005 and 2015. The research team also conducted nine focus groups in Southern California, Louisiana, Pennsylvania, and Ohio and at a national advocacy conference to ask about patients’ post-surgical experiences. A total of 76 patients with obesity participated in the focus groups.

Read more about this study at www.pcori.org/Arterburn218

Download this Evidence Update


Partner logos for the PCORI Evidence Update on Comparing Two Types of Weight Loss Surgery: The logos for PCORI and theObesity Action Coalition


1. © 2011–2021 Patient-Centered Outcomes Research Institute. “Comparing Three Types of Weight Loss Surgery -- The PCORnet Bariatric Study.” Last updated July 24, 2020. https://www.pcori.org/Arterburn218

2. Anau J, Arterburn D, Coleman KJ, et al. (2020). Comparing Three Types of Weight Loss Surgery -- The PCORnet Bariatric Study. Patient-Centered Outcomes Research Institute (PCORI). https://www.pcori.org/sites/default/files/Arterburn218-Final-Research-Report.pdf

3. Arterburn D, Wellman R, Emiliano A, et al. PCORnet Bariatric Study Collaborative. Comparative Effectiveness and Safety of Bariatric Procedures for Weight Loss: A PCORnet Cohort Study. Ann Intern Med. 2018 Oct 30. doi:10.7326/M17-2786

4. McTigue KM, Wellman R, Nauman E, et al. PCORnet Bariatric Study Collaborative. Comparing the 5-Year Diabetes Outcomes of Sleeve Gastrectomy and Gastric Bypass: The National Patient-Centered Clinical Research Network (PCORNet) Bariatric Study. JAMA Surg. 2020 Mar 4:e200087. doi:10.1001/jamasurg.2020.0087

5. Courcoulas A, Coley RY, Clark JM, et al. Interventions and Operations 5 Years After Bariatric Surgery in a Cohort From the US National Patient-Centered Clinical Research Network Bariatric Study. JAMA Surg. 2020 Jan. doi:10.1001/jamasurg.2019.5470

6. Arterburn D, Coleman K, Schlundt D, et al. Understanding the Bariatric Patient Perspective in the National Patient-Centered Clinical Research Network (PCORnet) Bariatric Study. Obes Surg. 2020 Jan 21; https://doi.org/10.1007/s11695-020-04404-8

7. Mechanick JI, Apovian C, Brethauer S, et al. Clinical Practice Guidelines for the Perioperative Nutrition, Metabolic, and Nonsurgical Support of Patients Undergoing Bariatric Procedures - 2019 Update: Cosponsored by American Association of Clinical Endocrinologists/American College of Endocrinology, The Obesity Society, American Society for Metabolic & Bariatric Surgery, Obesity Medicine Association, and American Society of Anesthesiologists – Executive Summary. Endocr Pract. 2019;25(12):1346–1359. doi:10.4158/GL-2019-0406

The information in this publication is not intended to be a substitute for professional medical advice. This update summarizes findings from a PCORI research award to Kaiser Permanente Washington Health Research Institute.

PCORnet® is intended to improve the nation’s capacity to conduct health research, particularly comparative effectiveness research (CER), efficiently by creating a large, highly representative network for conducting clinical outcomes research. PCORnet® has been developed with funding from PCORI®.

Posted: September 16, 2021

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