Fat Acts as a 'Reservoir' for COVID

A recent study found obese people with COVID-19 were 113% more likely to end up in a hospital, 74% more likely to be admitted to an ICU, and 48% more likely to die than people of a healthy weight, per Science. New research might explain why. The study, posted online in October but not yet peer reviewed, shows the coronavirus infects fat cells and immune cells within body fat, triggering a destructive inflammatory response. A person who is significantly above their ideal weight will have a lot of extra fat in which the virus can "hang out" and replicate, while awaiting an immune response that acts "like a perfect storm," Dr. David Kass, a professor of cardiology at Johns Hopkins, tells the New York Times. The more fat there is, the greater the problem.

"If you really are very obese, fat is the biggest single organ in your body," Kass says. And if infected with COVID-19, "it becomes kind of a reservoir." (This is also true with HIV and influenza, per the Times.) Looking at patients who died of COVID-19, researchers were able to see the coronavirus in fat tissue near various organs. In experiments using body tissue from bariatric surgery patients, they found the fat cells, or adipocytes, could themselves become infected. Pre-adipocytes, which mature into adipocytes, could not be infected but these still contributed to the strong inflammatory response produced by infected immune cells within fat, called adipose tissue macrophages. That inflammatory response is key.

"We're seeing the same inflammatory cytokines that I see in the blood of the really sick patients being produced in response to infection of those tissues," study author Dr. Catherine Blish of Stanford University Medical Center tells the Times. These cytokines occasion more inflammation and the release of more cytokines, which "could well be contributing to severe disease." It might also be contributing to long COVID, according to the study authors, who say we may need to adjust COVID vaccine and treatments in accordance with a person's weight and fat tissue. This is especially relevant in the US, where 42.4% of people are obese and 73.6% of people are overweight, per Fortune. (More COVID-19 stories.)