Why is obesity a risk factor for severe covid-19?
In July Public Health England estimated that having a BMI of 35 to 40 could increase a person’s chances of dying from covid-19 by 40%, while a BMI greater than 40 could increase the risk by 90%.
1 But why is this?
Stephen O’Rahilly, director of the Medical Research Council’s Metabolic Diseases Unit at the University of Cambridge, also speaking at the briefing, said, “Two things happen when obesity occurs: the amount of fat increases, but also you put fat in the wrong places. You put it in the liver and in skeletal muscle. And that disturbs metabolism. The key disturbance is that you get very high levels of insulin in the blood.”
This disturbance is associated with a range of abnormalities, including increases in inflammatory cytokines and a reduction of a molecule called adiponectin that directly protects the lungs, he says.
It’s also possible that fat increases in the lung itself, which may disturb how the lung handles the virus, he adds. “The simple stuff you read about—big chest, big bellies, et cetera—is all grossly oversimplistic. What is really going on is metabolic, and we know that because if we look at genetic markers for the metabolic disturbance they are much more closely related to the bad outcomes than genetic markers for obesity itself,” O’Rahilly says.