Associations between BMI and Covid-19 severity in 6·9 M people in England
thelancet.com
thelancet.com
The main datapoint is that for a BMI of 23, there is very little risk.
[0] https://www.thelancet.com/cms/10.1016/S2213-8587(21)00089-9/...
> We also found significant associations between presence of type 2 diabetes and severe COVID-19 outcomes, even after mutual adjustment for BMI in model 7 (table 2).