The risk of developing severe COVID-19 increases significantly with age. But since the pandemic began, there is mounting evidence that many of the most serious cases of the disease involve people with obesity—even if they’re young.
In the United States, this may be particularly worrisome since obesity rates have been rising for decades.Nearly half of American adults (42.4 percent) are obese, according to the Centers for Disease Control and Prevention (CDC). Meanwhile, 9.2 percent of Americans have severe obesity.
The obesity epidemic stems from many causes, such as where people live as well as their income level and ability to exercise. Whether or not people have access to healthy food or if anyone in their family has obesity can also increase risk. Taking medications that can result in weight gain could also contribute. This complexity means losing weight can be tough. It also makes this epidemic hard to fix.But why does obesity make people more vulnerable to severe COVID-19 infection? And what can you do about it?
Obesity is tied to severe COVID-19
People with severe COVID-19 often have chronic health issues linked to obesity, including heart disease and diabetes. But obesity, itself, counts as one of the underlying medical conditions that increases the risk for more serious infection. It also ranks among the top risk factors for hospitalization with the disease.
By definition, obesity develops when people’s weight is greater than what is considered healthy for their height. Body mass index (BMI) is a measure used to help determine if someone is obese. It’s calculated by dividing your weight in kilograms by your height in meters squared. (You can calculate your BMI here.) BMI is classified as the following:
- Overweight: BMI of 25 to less than 30
- Obese: BMI of 30 to less than 40
- Severely obese: BMI of 40 or higher
People with obesity may have triple the risk of hospitalization with COVID-19, compared to people without obesity, the CDC reports. Being severely obese may increase the risk by 4.5 times.
A July 2020 analysis of 75 studies in Asia, Europe and North and South America published in Obesity Reviews also found that people with obesity who were hospitalized with COVID-19 had 74 percent increased risk of admission to an intensive care unit (ICU) and 48 percent increased risk of death, compared to people without obesity.
Another large August 2020 study published in Annals of Internal Medicine, involving 6,916 people hospitalized with COVID-19 in Southern California, found that the risk of death increases in people with higher BMIs. Compared to people with normal BMI, the risk of death from COVID-19 was nearly 2.7 times higher in people with a BMI of 40 to 44, and more than four times higher in people with a BMI of 45 or greater. This risk was most striking among men and those aged 60 years or younger.
The largest study of its kind on this topic included 16,780 people hospitalized with COVID-19 across the U.S. Of these patients, 77.2 percent were overweight or obese. The study, which was conducted by the pharmaceutical company Genentech, was published as a pre-print and has not yet undergone peer review.
Being young may not offset the risk
Scientists are still learning about COVID-19. But so far, research suggests that children are less likely than adults to develop severe symptoms or die from the disease. This may be due, at least in part, to the fact that activity levels of proteins called ACE2 receptors, which help usher SARS-CoV-2 into cells that line the nasal cavity, are naturally lower in children. Kids also typically have a more robust innate, or initial immune response to the coronavirus than adults.
While older age is a risk factor for more severe SARS-CoV-2 infections, being obese can spell trouble for younger people, too.
A September 2020 study of 3,222 young adults between 18 and 34 years old who were hospitalized with COVID-19 across the U.S. found that 36.8 percent had obesity, and 24.5 percent had severe obesity. The researchers found that severe obesity was associated with 2.3 times increased risk of mechanical ventilation or death, compared to not being obese. Moreover, the study showed that 52.5 percent of those with obesity and nearly 41 percent of those with severe obesity required mechanical ventilation or died.
Among U.S. adults between 20 and 39 years old, 40 percent have obesity and 9.1 percent have severe obesity. Among adults between 40 and 59 years old, those percentages climb to 44.8 percent for obesity and 11.5 percent for severe obesity.
And the problem is increasingly affecting children. Obesity affects 13.9 percent of children between 2 and 5 years old, 18.4 percent of kids between 6 and 11 years old and 20.6 percent of 12- to 19-year-olds. All told, 18.5 percent of American children between the ages of 2 and 19 are obese, accounting for 13.7 million children.
So, while research on the effects of COVID-19 is ongoing, this could mean that some children and young adults may be at risk for a more severe infection if they develop COVID-19. Keep in mind, however, that other variables may come into play, such as kids’ genetics and whether or not they have other chronic health issues. Research also suggests that the expression of ACE2 in the lungs increases with age.
Why obesity matters
Obesity may worsen COVID-19 for a few reasons. First, obesity often goes hand in hand with other medical conditions, such as high blood pressure and diabetes, which are also tied to more severe COVID-19.
Obesity can also affect lung capacity and function, making it harder for mechanical ventilation to work.
Having a larger body mass and larger waist circumference can make it more difficult for doctors to perform potentially life-saving procedures in the hospital, such as intubation, which is used to improve oxygenation of the lungs. Obesity also increases the risk for obstructive sleep apnea and other respiratory issues, which could lead to worse outcomes for those with COVID-19.
Obesity, itself, may also lead to more severe infections, according to Melinda Beck, PhD, who conducts research on how obesity affects the ability of the immune system to fight off viruses.
Obesity basically hits the immune system with a double whammy, explains Beck, a professor in the department of nutrition at the University of North Carolina at Chapel Hill Gillings School of Global Public Health. It causes low-level underlying inflammation that’s chronic and always present—even in people without COVID-19, she says. This may result in more severe disease among those who do become infected.
“You get a hyper-inflammatory response in the lungs of people with obesity when they are first infected with COVID-19,” Beck says.
Several studies have shown that obesity is associated with chronic inflammation as well as reduced blood flow and increased risk for blood clots, which can result in insulin resistance, type 2 diabetes, high blood pressure, heart disease and a weakened immune system.
Obesity causes certain immune cells called T-cells, which help fight off infections, to not work as well as they should. So, these T-cells cannot fend off COVID-19 as well as they would in someone without obesity.
Ways to protect your health
It’s essential for everyone aged 6 months or older to get vaccinated against the flu. As concerns grow about a double threat of flu plus COVID-19, Beck advises people with obesity to “get your flu shot.”
Even if you come down with the flu after getting a flu shot, being vaccinated can decrease your chance of having a severe infection and being hospitalized.
Beck also advises that people with obesity take the same precautions against COVID-19 as everyone else: Wear a mask, stay away from crowds, wash your hands well and often, avoid touching your face with unclean hands and try to maintain at least six feet of physical distance from other people.
The CDC also advises people with obesity to eat a healthy diet, engage in physical activity, get enough sleep and try to cope with stress—all of which may help with weight loss and improve immune function.
For many, this is easier said than done. Losing weight and getting enough exercise can be hard even in normal times. COVID-19 hasn’t made it any easier. But incorporating some small, manageable healthy adjustments into your routine is a start and could help.
While scientists are still working to understand how to manage COVID-19, we know that losing excess weight has been shown to help improve other conditions associated with the coronavirus infection, like diabetes and heart disease.
“We would always say it’s better to lose weight,” Beck says. “We don’t have evidence yet, but it probably would help.”
Medically reviewed in September 2020.