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Doctors & Advice, Family Health

Obesity Emerges as Risk Factor for Severe COVID-19 Illness


Yale Medicine physicians explain how obesity may heighten chance of severe disease.

Advanced age has long been recognized as the leading risk factor for severe illness from COVID-19, but obesity—even among younger people—is emerging as a major concern.  

Ania Jastreboff, MD, PhD, a Yale Medicine endocrinologist and obesity medicine physician, says the evidence so far is worrisome.

“We all know that older age is the greatest risk factor. But obesity is emerging as one of the next most important ones,” says Dr. Jastreboff. “Additionally, if you consider other diseases implicated with COVID-19 severity such as type 2 diabetes, cardiovascular disease, or hypertension, obesity is a common contributor underlying all of them.”

And it looks like the excess weight itself is problematic, not just the other health conditions it causes. “Early data support that obesity is an independent risk factor, meaning that if you control for diabetes, heart problems, hypertension, and other medical conditions, obesity—itself a chronic disease—may potentially be the unifying disease involved in exacerbating COVID-19,” Dr. Jastreboff says.

In fact, one study out of New York City showed obesity was a stronger factor predicting hospitalization for COVID-19 than high blood pressure, diabetes, or cancer—or even pulmonary, kidney, or coronary disease

Another study, which looked at hospitalized COVID-19 patients under age 60 in New York City, found that individuals who have obesity were twice as likely to be hospitalized and even more likely to require critical care than those who do not have it.

Obesity is defined as having a body mass index (BMI, a value derived from someone’s height and weight) equal to or more than 30. Forty-two percent of American adults have obesity, according to the Centers for Disease Control and Prevention (CDC). Furthermore, nearly 50% of Blacks and 45% of Hispanics have obesity—of special concern, given that COVID-19 disproportionately affects these populations.

“To say certain races and ethnicities have a higher proportion of obesity would be too superficial,” says Albert Ko, MD, a Yale Medicine infectious disease specialist and an epidemiologist at Yale School of Public Health. “These are associations. What we really need to know is, what is it about obesity that makes people more likely to die from COVID-19? Do they get infected more easily? Is it something about their immune response? We know that people who have obesity have worse outcomes for a lot of different diseases, but is there something special about COVID?”

Questions remain about COVID-19 and obesity

Medical experts haven’t yet pinned down why obesity seems to make COVID-19 worse, but there are numerous theories. One reason may be related to the fact that obesity can cause a state of chronic, low-grade inflammation, says Kevan Herold, MD, a Yale Medicine endocrinologist and immunobiologist.

“The more severe manifestations of COVID-19 seem to be related to an inflammatory state, which suggests there may be some sort of link, but we don’t really understand why,” Dr. Herold says. “This is a rapidly moving field, with more data starting to come in.”

Lung function may be another factor. COVID-19 is known to cause respiratory disease, and those with obesity may already have reduced lung volume and capacity. Obesity is also an important risk factor in the development of acute respiratory distress syndrome (ARDS), a dangerous condition that can occur in severe COVID-19 cases.

Furthermore, obesity can complicate COVID-19 treatment. For instance, many hospitalized patients benefit from being in the prone position (lying on their stomach, which is believed to help open airways), but obesity can make this difficult.

“We don’t yet know whether someone with obesity or a higher weight may require different medications, at different doses, and at different time points; there is much to be learned,” Dr. Jastreboff adds.

Steps to take if you or a loved one has obesity

Obesity as an increased risk factor for COVID-19 could serve as a “wake-up call” for the country, Dr. Jastreboff says. “We’ve been ignoring obesity as a chronic disease and now we are faced with COVID-19, and we see that the pathophysiology of obesity may actually be exacerbating the severity of it,” she says.

For those who have obesity, there are small steps they may take to help manage weight, including finding ways to fit movement and physical exercise into the day or cooking at home, Dr. Jastreboff says.

But experts say that obesity is not just a matter of eating too much and exercising too little. Genetics, environment, dietary composition, and metabolic changes are all contributors to excess weight and obesity. “That’s why compassion and understanding, as well as interventions, such as treatment with anti-obesity medications, surgery, or other therapeutic options, are critical for patients with obesity,” adds Dr. Jastreboff. “And if we can help these individuals early on, perhaps we can help quell the overall severity of COVID-19.”

Dr. Ko agrees. “Right now, we are in the middle of a pandemic. But we also have an underlying obesity epidemic, which has affected our communities for some time," he says. "We must address this long-term public health threat, but right now, we need to take obesity seriously as a risk factor for COVID-19 and protect this potentially vulnerable population."

Learn about Yale's research and response efforts to COVID-19.