From the earliest days of the Covid-19 pandemic, it’s been obvious to doctors and researchers that obesity is a frequent factor among severely ill patients, as well as those who die, particularly in men.

The question for many was whether the cause was obesity itself, or ailments like heart disease and diabetes that are associated with carrying too much fat.

New studies appear to point to the answer: obesity alone increases the risk of severe sickness and death from the coronavirus.

And that ties in with the facts that the U.S. has accumulated far more Covid-19 cases than any other country (more than 6.3 million, as of Tuesday), as well as the largest number of pandemic deaths in the world (almost 190,000) — and that it’s high on the list of countries with the highest rates of obesity.

“In the United States, the obesity rate among adults has climbed for decades and is now at 42%. The rate is even higher among Black and Hispanic Americans,” reports the Associated Press.

Obesity seems to be tied to getting very sick from a coronavirus infection, and doctors are trying to figure out why. https://t.co/NtuJxDztIl

— AP Health & Science (@APHealthScience) September 8, 2020

“Researchers say multiple factors likely make it harder for people who are obese to fight a coronavirus infection, which can damage the lungs. Carrying around a lot of extra weight strains the body, and that excess fat could limit the lungs’ ability to expand and breathe,” the AP says. 

Obesity is also associated with chronic inflammation, which can undermine the body’s defenses against serious health threats, including viruses.

A recent analysis of thousands of patients in Southern California “identified extreme obesity as an independent risk factor for dying among Covid-19 patients — most strikingly, among younger and middle-aged adults 60 and younger, and particularly among men,” the New York Times reported.

Gender is a significant factor, as well.

Obese men tend to carry the most excess fat around their bellies, which puts them at higher risk of dying from Covid-19 than women who are just as overweight, but have different fat distribution.

“Complications in care can arise once hospitalized, too,” the AP says. “To help with breathing, for example, doctors have been putting patients hospitalized with Covid-19 on their stomachs. But that can be difficult for the obese, making it more likely they’re put on ventilators.”

And on top of all that, even after a vaccine is developed and tested, it might be less effective for the obese, as it is with the flu vaccine and others.