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Some researchers believe fat tissue itself may make COVID-19 worse.Reuters

As Jennifer Lighter made the rounds in her hospital’s intensive care unit, she was struck by two things. A number of the patients with severe COVID-19 were not as old as she would have expected, ranging from their late teens to their 40s and 50s. And many of the younger patients were overweight.

“It’s pretty shocking whenever you see a younger patient coming in, intubated and not doing well. So you think about those cases a lot,” said Dr. Lighter, a hospital epidemiologist and assistant professor in the department of pediatrics at NYU Langone Health in New York.

To determine whether their weight had anything to do with how ill they were, Dr. Lighter and her team conducted a study of 3,615 COVID-19 patients, accepted by the Clinical Infectious Diseases journal, that found those with obesity were twice as likely to require care in hospital, and some were three times more likely to be admitted into intensive care than those with a body-mass index (BMI) considered in the normal range. These patients did not have other health conditions that would put them at higher risk, she said.

This work is among a growing number of reports that suggest obesity can be a risk factor for severe COVID-19, independent of other risk factors such as age and underlying health problems including diabetes, hypertension and heart disease. While these risk factors are often related (obesity is associated with a higher risk of some of these other health problems), some researchers believe fat tissue itself may make COVID-19 worse.

Carrying extra fat "stresses the body and makes it harder to do stuff. But we’re learning the fat itself is biochemically active,” said David Kass, a professor of cardiology at Johns Hopkins University School of Medicine.

Dr. Kass explained the kind of fat that forms in your abdomen produces signalling molecules called cytokines that promote inflammation, part of the body’s immune response. The effect, he said, is like having an intrinsic cellular war constantly going on in the background. An infection of the new coronavirus is like dropping a bomb on top of it all, he said.

“The probability you’re gonna be able to withstand all of that is less,” he said.

In a correspondence paper, published in The Lancet this month, Dr. Kass and his team analyzed data on 265 patients in U.S. hospitals, with ages ranging from their teens to their 90s. They found those admitted to hospital who were younger were more likely to be obese. The median BMI was 29.3 kilograms per metres squared, just shy of 30, which is defined as the lower end of the obese range.

Dr. Kass said part of the issue may be mechanical. Having more fat mass in your abdomen can make it harder to move your diaphragm, thus making it harder to breathe. Another potential explanation is that fat cells may act like a depot or reservoir for the new coronavirus, which is known to bind to protein targets called ACE2, he added. These proteins are highly expressed, or deposited, on fat cells, he said.

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While he did not know how the virus affects fat cells, Dr. Kass suggested fat ”may well be kind of like a shelter zone for the virus to exist for a longer period of time.”

Arya Sharma, a professor of medicine at the University of Alberta and scientific director of Obesity Canada, said an increased risk for people with obesity is something experts previously saw during the SARS and H1N1 epidemics.

“When they get ill, they tend to have more complications, more respiratory disease,” he said, adding when they end up in hospital, it can take them longer to recover.

Dr. Sharma emphasized, however, that many individuals with obesity, like others, who are infected with the new virus, never show symptoms or have only mild symptoms. And even among those who require hospital care, many do recover.

“It’s not as though obesity is somehow your death sentence,” he said.

Dr. Lighter pointed out that the risk to people with obesity was not found to be multiple times higher than others. But when jurisdictions gradually emerge from the lockdown, she suggested that as part of the high-risk group, people with obesity may be among the last to see restrictions lifted. She added that once therapeutics for COVID-19 become available, patients with obesity are among those who should be targeted for early treatment to prevent severe infection.

For Dr. Sharma, the higher risk of COVID-19 among people with obesity highlights two concerns. First, he said, individuals with obesity tend to be treated less professionally by all kinds of health care workers. This discrimination can mean people wait longer or be less likely to seek medical help if they become ill, he said. Second, it underscores how undertreated obesity is in the first place.

“With or without COVID-19, we need to take obesity seriously,” he said.

Now that it is recommended you wear a face covering in dense public settings like grocery stores and pharmacies, watch how to make the three masks recommended by the Centers for Disease Control and Prevention. Written instructions available at

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