It’ll cost less than the effects of obesity
Moral hazard has never been a good reason for any sort of regulation, the same principle can be used to justify not covering motorcycle riders, people who trad climb, people who do snow sports, people who jaywalk, people who work at a desk and drive everywhere, etc etc etc
Thats like your opinion man. I personally don't want to pay for gluttony via my tax dollars. I don't care about smokers, junkies, or gambling addicts. If people want to donate to some ozempic fund, by all means.
And, motorcycles require special insurance, as does high-risk recreational sports like climbing. If you drive/commute to work, thats factored into your premiums. If you get hit by a car jaywalking, that is usually on you. Those examples have nothing to do with the prospect of tax-funded anti-fat pills.