at least there's a study now, look for "Study shows COVID-19 induces body fat and other metabolic changes"

"...The study uncovered that despite following a weight-control diet and consuming fewer calories, the TF% of COVID-19 patients surged over 2% after infection. They also had elevated fasting blood glucose, insulin, and IR compared to uninfected controls.

Future studies should investigate the possible mechanism governing changes in TF% and FFM in COVID-19 subjects. Nevertheless, the study findings could inform customized nutrition therapy to improve COVID-19 outcomes."