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Can Bariatric Surgery Reduce COVID-19 Severity?

  • Authors: News Author: Mitchel L. Zoler, PhD; CME Author: Laurie Barclay, MD
  • CME / ABIM MOC / CE Released: 2/23/2022
  • Valid for credit through: 2/23/2023, 11:59 PM EST
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Target Audience and Goal Statement

This activity is intended for diabetologists/endocrinologists/metabolic medicine clinicians, family medicine/primary care clinicians, infectious disease clinicians, internists, nurses, pharmacists, public health officials, and other members of the healthcare team for patients in whom weight loss (bariatric or metabolic) surgery may be indicated.

The goal of this activity is to describe the association between successful weight loss achieved by bariatric surgery and the improvement in COVID-19 related outcomes in patients who suffered from obesity, according to a cohort study of adults with body mass index (BMI) ≥ 35 kg/m2 who underwent weight loss surgery between January 1, 2004, and December 31, 2017 at Cleveland Clinic Health System (CCHS).

Upon completion of this activity, participants will:

  • Describe the association between successful weight loss surgery and improved risk and severity of COVID-19 in patients with obesity (BMI) ≥ 35 kg/m2, according to a cohort study from CCHS.
  • Identify clinical implications of the association between successful weight loss surgery and improved risk and severity of COVID-19 in patients with obesity, according to a cohort study from CCHS
  • Outline strategies and the implications for the Interprofessional healthcare team to deliver the highest quality of care


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News Author

  • Mitchel L. Zoler, PhD

    Freelance writer, Medscape


    Disclosure: Mitchel L. Zoler, PhD, has disclosed no relevant financial relationships.

CME Author

  • Laurie Barclay, MD

    Freelance writer and reviewer
    Medscape, LLC


    Disclosure: Laurie Barclay, MD, has disclosed the following relevant financial relationships:
    Own stock, stock options, or bonds from the following ineligible company(ies): AbbVie Inc. (former)

Editor/Nurse Planner

  • Leigh A. Schmidt, MSN, RN, CMSRN, CNE, CHCP

    Associate Director, Accreditation and Compliance
    Medscape, LLC


    Disclosure: Leigh A. Schmidt, MSN, RN, CMSRN, CNE, CHCP, has disclosed no relevant financial relationships.

CME/CE Reviewers

  • Esther Nyarko, PharmD

    Director, Accreditation and Compliance
    Medscape, LLC


    Disclosure: Esther Nyarko, PharmD, has disclosed no relevant financial relationships.

  • Yaisanet Oyola, MD

    Associate Director, Accreditation and Compliance, Medscape, LLC


    Disclosure: Yaisanet Oyola, MD, has disclosed no relevant financial relationships.

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Can Bariatric Surgery Reduce COVID-19 Severity?

Authors: News Author: Mitchel L. Zoler, PhD; CME Author: Laurie Barclay, MDFaculty and Disclosures

CME / ABIM MOC / CE Released: 2/23/2022

Valid for credit through: 2/23/2023, 11:59 PM EST


Note: The information on the coronavirus outbreak is continually evolving. The content within this activity serves as a historical reference to the information that was available at the time of this publication. We continue to add to the collection of activities on this subject as new information becomes available. It is the policy of Medscape Education to avoid the mention of brand names or specific manufacturers in accredited educational activities. However, manufacturer names related to COVID-19 vaccines may be provided in this activity to promote clarity. The use of manufacturer names should not be viewed as an endorsement by Medscape of any specific product or manufacturer.

Clinical Context

In patients with obesity, bariatric surgery may cause substantial, durable weight loss; improved cardiometabolic risk factors; survival benefit; and amelioration of obesity-related inflammatory state. Obesity is linked to poor COVID-19 clinical outcomes.

Study Synopsis and Perspective

People with obesity who had substantial weight loss after metabolic (bariatric) surgery had a lower risk for severe complications from COVID-19 compared with matched people with obesity who did not undergo surgery and did not have a similarly high level of weight loss.

The results from an observational, retrospective review of nearly 12,000 patients from a single US center showed that people with obesity who underwent metabolic surgery lost, on average, nearly 19% more body weight than did matched control individuals with obesity who did not have surgery during median follow-up of almost 8 years.

Among the nearly 800 people from the study group who developed COVID-19 during the first year of the pandemic, individuals who underwent metabolic surgery had a 49% lower risk for hospitalization, a 63% reduced risk for the need for supplemental oxygen, and a 60% lower risk for "severe" COVID-19 when compared with the control group. Severe COVID is defined as the need for mechanical ventilation or death. All-cause death alone was 73% lower among the people who had surgery, but this difference was not significant (P = .09).

Obesity Is a "Modifiable Risk Factor" for Severe COVID-19

The results "clearly demonstrate that obesity is a modifiable risk factor" for more severe exacerbations of COVID-19, said Ali Aminian, MD, first author of the report, published online on December 29.[1]

"It's not feasible to conduct a randomized trial on large numbers of patients with obesity to assess COVID outcomes following a weight loss intervention," noted Aminian, professor of surgery and director of the Bariatric and Metabolic Institute at the Cleveland Clinic, in Cleveland, Ohio.

"Therefore, these data provide the best available evidence" on the effect of substantial and maintained weight loss and the risk for more severe complications of COVID-19, Aminian said in an interview.

"COVID-19 should now be added to the long list of obesity comorbidities that can be mitigated by metabolic surgery," concluded an invited commentary that accompanied the new study.[2]

The new evidence strongly suggests "that substantial weight loss reduces the obesity-associated risk for severe COVID-19 in people who become infected," commented Lee M. Kaplan, MD, PhD, director of the Weight Center at Massachusetts General Hospital in Boston, Massachusetts, who was not involved with the study.

It's "a very good study that makes a compelling argument," he added. "A prospective, randomized study may never be done, so you need to go with the data you have, and these are good data."

Another notable finding was that COVID-19 rates were roughly identical among the people who had undergone metabolic surgery and the control patients who had not, with both groups showing infection rates during March 2020 to March 2021 of about 9%.

"The risk of getting infected was the same, but with a much lower rate of complications" among those who had metabolic surgery and subsequent weight loss," said Steven E. Nissen, MD, senior author of the study and chief academic officer of the Heart, Vascular and Thoracic Institute at the Cleveland Clinic.

It Is All About the Weight Loss

The downshift in complications is likely "about weight loss, not about surgery," Nissen added in an interview. "If a person lost [a similar amount of] weight by another means, I think they would very likely get the same benefit," although he acknowledged that the new study does not provide direct evidence for this.

"People who are obese become sicker when they have COVID-19 infection. If a person loses weight, they will have less risk" for exacerbations of their infection, Nissen predicted.

"This is another good reason to treat obesity. The study shows that substantial weight loss is worthwhile," although lessening of COVID-19--related complications is just one more of what were already greater than 200 different comorbidities proven to improve when people with obesity lose weight, noted Kaplan.

As a result, he was skeptical that this new evidence will have much impact on the number of people with obesity seeking bariatric surgery or other means for achieving substantial weight loss. Even before COVID-19, there was good evidence for the "enormous value of effectively treating obesity," Kaplan said in an interview.

Kaplan also agreed that substantial weight loss induced by other strategies, such as treatment with potent weight-loss agents that include semaglutide, tirzepatide, and cagrilintide (the latter two still under investigation), likely has a similar impact.

"The study shows that substantial weight loss can mitigate COVID-19 complications. Today, that weight loss is best achieved using bariatric surgery, but in the future," various new drug interventions may produce similar results, Kaplan said.

Study Details

The study began with the entire cohort of more than 675,000 patients seen at the Cleveland Clinic during 2004 to 2017 who had at least 1 record of measured body mass index (BMI) ≥ 35 kg/m2. From this group, the researchers identified more than 5000 patients who underwent metabolic surgery and more than 15,000 matched control participants who did not undergo surgery.

Comparison between these two groups showed that during a median 7.6-year follow-up, the average incremental weight loss among the people who had surgery compared with people who did not have surgery was an 18.6-percentage point reduction from baseline body weight.

From this starting cohort of just over 20,000 total patients, 2958 from the surgery group and 8851 of the control participants were available for assessment of their COVID-19 status during the 12-month period of March 1, 2020 to March 1, 2021. During this 12-month time window, 206 patients in the surgical group and 578 control participants developed COVID-19. At the time of their positive SARS-CoV-2 test result, the average weight of the infected patients who had undergone surgery was 108.4 kg and 128.4 kg among the infected control participants.

The study was funded by a grant from Medtronic, Inc. Aminian has received grant support and speaking honoraria from Medtronic, Inc. Nissen has received research funding from AbbVie Inc; Amgen Inc.; AstraZeneca Pharmaceuticals LP; Bayer HealthCare Pharmaceuticals; Bristol-Myers Squibb Company; Esperion Therapeutics, Inc.; Lilly; Novartis Pharmaceuticals Corporation; and Silence. Kaplan has been a consultant to Amgen Inc.; Ethicon, Inc.; Gelesis; Lilly; Novo Nordisk; Pfizer Inc.; Rhythm Pharmaceuticals; and Xeno Pharmaceuticals.

JAMA Surg. 2021 Dec 29; doi: 10.1001/jamasurg.2021.6496

Study Highlights

  • The study cohort included 20,212 adult patients (median age = 46 [interquartile range (IQR), 35-57] years); 77.6% female) with BMI ≥ 35 (45; 41-51) kg/m2 at CCHS.
  • Patients in the surgical group (Roux-en-Y gastric bypass or sleeve gastrectomy between January 1, 2004 and December 31, 2017) were matched 1:3 by BMI and other factors to patients with obesity but no surgery (control group).
  • Follow-up was conducted through March 1, 2021 (median duration = 6.1 [IQR, 3.8-9] years).
  • Distinct outcomes were examined before and after COVID-19 outbreak on March 1, 2020.
  • Weight loss and all-cause mortality were assessed between enrollment and March 1, 2020.
  • Before the COVID-19 outbreak, surgical vs control patients lost more weight (mean difference at 10 years from baseline: 18.6% [95% CI: 18.4, 18.7]; P < .001) and had 53% lower 10-year cumulative incidence of all-cause non--COVID-19 mortality (4.7% [95% CI: 3.7, 5.7] vs 9.4% [95% CI: 8.7, 10.1]; P < .001).
  • 11,809 of 20,212 patients were available for assessment of COVID-19--related outcomes between March 1, 2020 and March 1, 2021.
  • Average weight was 108.4 kg among 206 infected surgical patients and 128.4 kg among 578 infected control participants, and the former also had better glycemic control.
  • Rates of positive SARS-CoV-2 test results were similar in both groups (9.1% [95% CI: 7.9, 10.3] vs 8.7% [8, 9.3]; P = .71).
  • Bariatric surgery was associated with lower risks for hospitalization (adjusted hazard ratio [aHR] = 0.51 [95% CI: 0.35, 0.76]; P < .001), need for supplemental oxygen (0.37 [95% CI: 0.23, 0.61]; P < .001), and severe COVID-19 (a composite of ICU admission, need for mechanical ventilation, or death; 0.4 [95% CI: 0.18, 0.86]; P = .02).
  • The investigators concluded that among patients with obesity, substantial weight loss from surgery was associated with improved outcomes of COVID-19, suggesting that obesity can be a modifiable risk factor for severity of COVID-19.
  • COVID-19 should now be included in the long list of obesity comorbidities that can be ameliorated by metabolic surgery.
  • As it is not feasible to conduct a randomized trial on large numbers of patients with obesity to evaluate COVID outcomes after weight loss intervention, these findings provide the best available data on the effect of substantial, maintained weight loss and risk for more severe COVID-19.
  • Patients who underwent bariatric surgery were generally healthier at the time of contracting SARS-CoV-2, which may improve clinical outcomes.
  • Surgically induced weight loss may favorably affect the proinflammatory, prothrombotic disease process of COVID-19 by mitigating obesity-mediated hyperinflammation, hypercoagulopathy, and metabolic derangements.
  • Improved mechanics of breathing and lung physiological functions; better glycemic control; lowered hypertension and risk for comorbidities, including cardiac disease, sleep apnea, and kidney function, may also be involved.
  • Given limited COVID-19 therapies, patients with substantial, sustained weight loss were likely physically and physiologically better equipped to cope with an infection that may cause multiorgan involvement.
  • Weight loss of similar magnitude by nonsurgical intervention would likely provide the same benefit, although this study offers no direct evidence of this.
  • As people who are obese become sicker with COVID-19, weight loss by any means is likely to lower risk for COVID-19 exacerbations.
  • Obesity requires multidisciplinary, individualized management, including lifestyle and behavioral interventions, pharmacotherapy, and weight loss surgery.
  • Given study limitations of observational design and relatively low number of infections, the findings should be considered as hypothesis-generating and not conclusive, but the consistency of the sensitivity analyses results and the large observed magnitude of the risk reductions support the data’s robustness.

Clinical Implications

  • Among patients with obesity, substantial weight loss from bariatric surgery was associated with improved outcomes of COVID-19.
  • Implications for the Healthcare Team: COVID-19 should now be included in the long list of obesity risk factors.
  • Therefore, collaboration among the interprofessional health care team can be used as a strategic tool to deliver the highest quality of care.


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