Obesity is the biggest factor driving New York City's coronavirus hospitalizations after age

• In the largest study so far of US hospital admissions for COVID-19, researchers found that obesity was the single biggest chronic risk factor for admission, ahead of heart and lung diseases.
• Age remained the biggest predictor overall that someone was admitted to the hospital.
• Earlier research and anecdotes have suggested that America's obesity epidemic could make the coronavirus pandemic more complicated and, some predicted, deadlier.
• While weight and BMI are imperfect metrics of health, there are physiological reasons why excess body fat can complicate the respiratory illness.
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Since the coronavirus pandemic touched down in the US, health experts warned that the virus would hit some populations hardest - namely, older adults and those with underlying conditions like heart and lung disease.

But now, it appears a different population, people with obesity, may be even more at risk for serious illness from COVID-19 than those with heart and lung disease.

In the largest study so far of US hospital admissions for the virus, researchers in New York City found that having a body mass index over 30, which is considered obese, was the single biggest factor for admission aside from age.

Though the report was released as a preprint and has yet to undergo peer review, it provides further evidence for what earlier research and plenty of anecdotes have forecasted: America's obesity epidemic and the coronavirus pandemic could be a volatile storm.

The researchers looked at more than 4,103 COVID-19 patients

For the study, researchers at the NYU Grossman School and doctors at the NYU Langone Health center looked at the electronic patient records of 4,103 COVID-19 patients in the New York City healthcare system between March 1 and April 2.

They wanted to better understand which patients were most likely to be hospitalized to better inform triage decisions and to help other cities prepare for outbreaks based on their own demographics, among other reasons.

They found that about half of the 4,103 patients were admitted to the hospital, mostly determined by age and BMI. Specifically, 87% of patients who were over 65 were admitted to the hospital and 70% of those who were obese and over age 35 were admitted. Even those under 35 were more likely than not to be admitted if they were male and obese.

The researchers suggest this is due to obesity's inflammatory role in the body.

Past research and reports have warned that America may suffer from COVID-19 more due to its obesity epidemic

The US has an obesity rate of 42% compared to China's 6% and Italy's 10%. That's had some experts concerned about COVID-19 would hit there.

Some earlier research has reflected those fears.

A report out April 8 from the Centers for Disease Control and Prevention, for one, found that 48.3% of all patients admitted to the hospitals in 99 counties across the US were obese, and 59% of the 18- to 49-year-olds who were hospitalized were obese. That's startling compared to 40% of 20- to 39-year-olds in the general population who have obesity.

Another not-yet-peer-reviewed study in the Lancet, made available April 1, found that COVID-19 patients in China who were overweight had an 86% higher likelihood of developing severe pneumonia than their normal weight counterparts. Those who were obese were 2.4 times more likely to develop it.

As such, the Centers for Disease Control and Prevention has listed "severe" obesity, or a body mass index of 40 or over, as high-risk condition for the illness.

Excess body weight can burden the immune system and lung function

While weight and BMI are imperfect metrics of health, they are linked to other conditions like heart disease and diabetes that, on their own, increase the risk of serious illness from COVID-19.

Obesity's inflammatory response can also affect the immune system and lung function, both of which are critical in fighting COVID-19.

"At the immunological system level, the human body is extremely poorly adapted to chronic caloric overload," Dr. Gregory Poland, an infectious disease expert at the Mayo Clinic, previously told Business Insider. "It's as bad for our immune system as malnutrition is."

Extra weight around the chest and in the belly can also physically restrict breathing, which can be dangerous with a respiratory condition like COVID-19.

"Prior to COVID-19, we already knew that obesity is a risk factor for infection in general and more severe complications, and this is particularly true for respiratory infections," Poland said.

During the 2009 H1N1 epidemic in 2009, adults with body mass indexes over 30 were 3.1 times more likely to die from the infection than people of lower weights, while adults with body mass indexes over 40 were 7.6 times more likely to die.

"It's a difficult situation and an emotional situation since people who are in a certain BMI range are discriminated against. They're right to feel attacked and marginalized," Fatima Fakhoury, a weight-inclusive registered dietitian in New York, previously told Business Insider. "But in this case, as one example, if somebody in a couple is obese and somebody is not, they both need to be aware that one of them is high risk, and so maybe take extra precautions."

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