Proof That Substantial Weight Loss Lessens COVID-19 Severity

Mitchel L. Zoler, PhD

December 29, 2021

People with obesity who had substantial weight loss following metabolic (bariatric) surgery had a lower risk of 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, those who underwent metabolic surgery had a 49% lower risk of hospitalization, a 63% reduced risk of the need for supplemental oxygen, and a 60% lower risk of "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.

"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. "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.

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, 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 controls 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's 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 (Wegovy), tirzepatide, and cagrilintide (both still investigational), 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 2004–2017 who had at least one record of measured body mass index of at least 35 kg/m2. From this group, the researchers identified more than 5000 patients who underwent metabolic surgery and more than 15,000 matched controls 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 those 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 controls 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 controls 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 controls.

The study was funded by a grant from Medtronic. Aminian has received grant support and speaking honoraria from Medtronic. Nissen has received research funding from Abbvie, Amgen, AstraZeneca, Bayer, Bristol Myer Squibb, Esperion, Lily, Novartis, and Silence. Kaplan has been a consultant to Amgen, Ethicon, Gelesis, Lilly, Novo Nordisk, Pfizer, Rhythm, and Xeno.

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

Mitchel L. Zoler is a reporter with Medscape and MDedge based in the Philadelphia region. @mitchelzoler.

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