Obesity is a strong independent risk factor for COVID-19, the disease caused by the SARS-CoV-2 virus. Previous research has shown that people with obesity generate fewer antibodies in response to viral infection or vaccination; however, whether antibody quality is also affected by obesity is unknown. Findings published in a new report show that the majority of the antibodies found in people with obesity are autoimmune and not able to neutralize the SAR-CoV-2 virus, putting individuals with obesity at greater risk of severe COVID-19.

Obesity increases the rate of inflammaging, the process of chronic low-grade inflammation that wears down the body’s tissues over time, putting people with obesity at greater risk of many diseases. Inflammaging increases the risk of autoimmunity by increasing the concentration of damaged cellular components in the blood, potentially triggering the immune system to generate antibodies against its own cells. Previous research has shown that many patients with severe COVID-19 generate autoimmune antibodies that increase the risk of long-term complications. Because people with obesity experience increased baseline inflammaging, they may be at greater risk of developing long-term autoimmune complications for COVID-19; however, no published studies have yet addressed this concern.

The investigators collected blood from 15 participants with a lean BMI (less than 25) and 15 participants with an obese BMI (greater than 30) who tested positive for SARS-CoV-2. The investigators also collected blood from 30 participants who had not had a SARS-CoV-2 infection and were matched for age, sex, and BMI. The researchers measured the concentration of neutralizing antibodies (meaning antibodies that bind to the SARS-CoV-2 spike protein and prevent viral entry into cells), non-neutralizing antibodies, and autoimmune antibodies.

Participants with obesity had fewer SARS-CoV-2 antibodies than participants with a lean BMI, confirming previous reports. While all 15 SARS-CoV-2-positive participants with a lean BMI had circulating neutralizing antibodies, only a few participants with obesity did. The researchers found that SARS-CoV-2 infection increased the concentration of autoimmune antibodies in all patients, but the concentration of autoimmune antibodies was always higher in participants with obesity. Finally, they found that participants with the highest concentration of autoimmune antibodies also had the highest levels of serum C-reactive protein, a marker of chronic inflammation, suggesting that inflammation is integral to developing autoimmunity.

These data confirm previous reports that obesity reduces the effectiveness of the immune response in COVID-19 patients and increases the risk of autoimmunity.

• Link to full publication.

• Learn more about the risks of COVID-19 in people with and without obesity in this episode featuring Dr. Roger Seheult.