Obesity May Alter Immune System Response to COVID-19

Obesity may change a person's immune response to COVID-19, making it more difficult to fight off the virus and increasing the risk of complications, according to recent commentary published in Endocrinology.

The authors note that obesity can cause endocrine changes that may drive varied responses to the virus, including:

• Hormone regulation
• Hyperglycemia
• Tissue dysfunction
• Shifts in immune regulators like cytokines and leukocytes

End of the Obesity Paradox?

Previous studies have noted that there are some acute illnesses in which people who are obese have lower mortality rates, leading researchers to call this effect the "obesity paradox."

For example, one study looking at older Americans hospitalized with sepsis—a potentially life-threatening infection—found that obesity was associated with reduced mortality compared to those in both normal and overweight categories.

But COVID-19 may be the exception to the paradox, researchers in the recent commentary noted.

The reason is most likely tied to the way carrying higher amounts of weight tends to elevate inflammation levels. When that happens, it can cause a negative reaction in the immune system when faced with potential infections, according to study co-author Kanakadurga Singer, MD, associate professor and pediatric endocrinologist at the University of Michigan.

"One part of the immune system, the macrophage, may be key in driving severe COVID-19," she says. "Obesity may cause significant changes in macrophage function due to inflammation, and that could certainly play a role in higher risk of infection, and more risk of severe complications if that happens."

Other Factors at Play

Although inflammation may be crucial in terms of disease progression, it's likely not the only factor when it comes to possible connection between obesity and COVID-19 risk.

For instance, many people with obesity tend to have underlying conditions which have already been associated with greater COVID-19 risk by the Centers for Disease Control (CDC). Those can include:

• Heart conditions
• Lung disease and other respiratory issues
• Diabetes
• Liver disease, particularly non-alcoholic fatty liver disease
• Kidney disease

A particular concern is that obesity can limit respiratory function even in the absence of disease. Because of that, when faced with a respiratory virus like COVID-19, those with obesity may have more trouble than those without limited function, says Jennifer Lighter, MD, specialist in pediatric infectious disease at NYU Langone Health in New York.

"Any disease that has a respiratory element to it like flu or pneumonia tends to be more severe with obesity," she says. "That means if someone has obesity and tests positive for coronavirus, it's worth watching their disease progression very closely, especially if they begin to become short of breath."

Need for More Research

The recent commentary adds to research done this year on the issue of obesity and coronavirus, although no large-scale studies have been published yet. But smaller studies are indicating that obesity could be a major factor for risk.

For example, research in Nature Reviews Endocrinology in April noted that of 24 critically ill patients with COVID-19, 13 had obesity and 7 were overweight.

Researchers added that the sample size was too small for meaningful analysis, but did point out that 85% of those with obesity required ventilation and 62% didn't survive the illness.

"At this point, there's still a great deal we're learning about this virus as it progresses," says Katherine Araque, MD, endocrinologist and director of endocrinology of the Pacific Neuroscience Institute at Providence Saint John's Health Center in Santa Monica, California. "But anecdotally, we're hearing that patients with obesity are experiencing more severe complications at a younger age, and that's a concern."

Next Steps

For those who have obesity, studies and commentaries like these underscore the importance of keeping your immune system strong so it's better able to handle an infection if you're exposed. In addition to losing weight if possible, other strategies include:

• Handling stress and implementing mindfulness techniques
• Getting adequate, quality sleep
• Eating more fruits and vegetables
• Controlling chronic conditions like diabetes with medication adherence
• Get regular physical activity

These are good tips for everyone, not just those dealing with obesity.