Why COVID-19 is more deadly in people with obesity—even if they’re young

Fat cells secrete several inflammation-triggering chemical messengers called cytokines, and more come from immune cells called macrophages that sweep in to clean up dead and dying fat cells. Those effects may compound the runaway cytokine activity that characterizes severe COVID-19. “You end up causing a lot of tissue damage, recruiting too many immune cells, destroying healthy bystander cells,” says Ilhem Messaoudi, an immunologist who studies host responses to viral infection at the University of California, Irvine.