A recent study has shown that SARS-CoV-2, the virus that causes COVID-19, is capable of directly infecting fat cells and immune cells within body fat, which can lead to devastating consequences.
The Stanford University study—which has not yet been peer-reviewed or published in a journal—was posted online in late October on the preprint server bioRxiv.
What Research Shows
For the study, the researchers conducted lab experiments on fat tissue that had been taken from bariatric surgery patients. The goal was to see whether the tissue could be infected with SARS-CoV-2. Then they analyzed how different types of fat cells responded to the virus.
The researchers discovered that not only could the fat cells become infected by the COVID virus, but that immune cells called macrophages—which are found in tissues throughout the body, including fat (adipose tissue)—can also become infected and contribute to an inflammatory response in the body.
When the researchers analyzed fat tissue from the bodies of patients who had died of COVID, they found SARS-CoV-2 particles in the fat that was near various organs, including the lungs and heart.
The researchers concluded that the study’s findings “indicate that adipose tissue supports SARS-CoV-2 infection and pathogenic inflammation and may explain the link between obesity and severe COVID-19.”
The new study is not the first to demonstrate that SARS-CoV-2 can infect fat cells. Research published in Cell Metabolism in September reached similar conclusions. The study’s authors wrote that the data suggested that “SARS-CoV-2 may trigger adipose tissue dysfunction to drive insulin resistance and adverse outcomes in acute COVID-19.”
Weight in the U.S.
Obesity is common in the United States, and rates are dramatically increasing. Current data show that rates in the U.S. jumped from 30.5% (1999 to 2000) to 42.4% (2017 to 2018). Severe obesity also increased from 4.7% to 9.2% during the same time.
Statistics also demonstrate that being obese affects some racial and ethnic groups more than others. Non-Hispanic Black adults have the highest rates of obesity (49.6%), followed by Hispanic adults (44.8%), non-Hispanic White adults (42.2%), and non-Hispanic Asian adults (17.4%). Some scientists attribute these differences to systemic racism.
The rates of obesity in the U.S. also vary by age: 40% in adults aged 20 to 39 years, 44.8% in adults aged 40 to 59 years, and 42.8% in adults aged 60 and older.
Weight and COVID-19
According to the Centers for Disease Control and Prevention (CDC), obesity can triple your risk of being hospitalized with COVID-19. It’s also linked to impaired immune function and decreased lung capacity and reserve. Being severely overweight can also make it more difficult to ventilate the lungs.
Data from the CDC has shown that the risk of hospitalization, intensive care unit (ICU) admission, invasive mechanical ventilation, and death were greater as a COVID patient’s body mass index (BMI) increased.
A study published in the Journal of the American Heart Association in February 2021, which included more than 900,000 adult COVID-19 hospitalizations in the U.S. from the start of the pandemic to November 18, 2020, found that about 30.2% of those hospitalizations were linked to being obesity.
What Doctors Think
Experts are hesitant to draw too many conclusions about body fat and COVID in the absence of more data—especially since the new study is only preliminary.
Even though it is a biased measure, BMI is still widely used in the medical community because it’s an inexpensive and quick way to analyze a person’s potential health status and outcomes.
“The study has not undergone peer review and has not been published in a medical journal yet,” infectious disease expert Amesh A. Adalja, MD, a senior scholar at the Johns Hopkins Center for Health Security, told Verywell.
However, Adalja added that “the study results provide a basis for possibly understanding the linkage of obesity with severe COVID; that the virus is infecting fat cells and prompting them to release inflammatory molecules.”
Thomas Russo, MD, professor and chief of infectious disease at the University at Buffalo medical school, told Verywell that researchers already knew that some pathogens, such as influenza viruses, can infect body fat. Russo says, “if you’re obese—particularly morbidly obese—you’re more likely to have severe disease.”
Experts have hypothesized that the link is between obesity and underlying medical conditions like diabetes and chronic obstructive pulmonary disease, raising a person’s risk for severe COVID and numerous other diseases and complications.
Russo said that while the new study is “interesting and biologically plausible,” more research is needed before firm conclusions can be drawn.
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