against covid, it's vaccination. And it's not even close. It is both preventive and protective.
It's the most quick, predictable, and universally attainable protective measure for anyone over the age of 12. If you want to have a discussion about the #2 best variable to modify/influence to protect against severity of infection, then obesity/overweight certainly merits discussion. Same perhaps with type 2 diabetes or a handful of other medical conditions.
No one gets moderated for saying weight loss can help protect against severe covid symptoms. But if moderation was fact-checking, then they would be if they said it was the most important thing to do to protect against covid because it is simply not.