Obesity isn’t transmissible, so far as anyone knows. (With the possible exception of fecal transplants, but those are deliberate so any comparison of that to Covid would be BS).

And obesity doesn’t spike up at random intervals with enough extra hospitalisation to impede the healthcare system as a whole.

And obesity can’t be mostly prevented by getting a tiny low-risk jab in the arm every so often.

And they’re working on self driving cars precisely because it’s such a big cause of death, but those things are currently about as ready as a cure for aging. (As in: yes, but with huge caveats that make it a no in practice).