There are other risk factors, but being over weight or obese has been one of the greatest, especially for younger people.
https://www.cdc.gov/obesity/data/obesity-and-covid-19.html
Oh wow!
-Having obesity may triple the risk of hospitalization due to a COVID-19 infection.
-Obesity is linked to impaired immune function.2,3
-Obesity decreases lung capacity and reserve and can make ventilation more difficult.4
-As BMI increases, the risk of death from COVID-19 increases.
Studies have demonstrated that obesity may be linked to lower vaccine responses for numerous diseases (influenza6, Hepatitis B7,8,9, tetanus10).