I don't think GLP-1s are particularly expensive, so my top preference would be to just see them easily available. While not quite the same, it's a win that Rogaine/Minoxidil were once prescription-only but for a long time now can be bought at any grocery store and taken to the self-checkout. Still, I think the subsidy approach has been done for smoking problems via nicotine products before, and e.g. nicotine gum cost never seemed that high to me (especially compared to cigarettes).
But it's also worth remembering the relative risks involved. Obesity isn't quite the ticking time bomb / public menace it's often made out to be... For smoking, you'll find studies with relative risk numbers for lung cancer over 5 for casual 1-4 times a day smokers, and the number quickly exceeds 20 for heavier smokers. In contrast, with obesity, the most severe relative risks for things like heart disease or diabetes you'll find topping out around 4 to 5 for the most obese, even then often under 3, with milder 1.1 to 2 for the bulk of obese people. (Here, ~31% of the US has BMIs between 30-40, and ~9% have BMIs over 40.) For other harms, like there was a study on dementia a few years back, you'll also find pretty mild (1.1ish) relative risks, but these end up being similar with other factors like "stress", "economic status", or "low educational attainment". Just some thought for people thinking about subsidizing or providing free stuff, the cost tradeoff with paying for other things later might not work out so neatly, and there's reason to not focus solely on obesity but also do the same sort of analysis with other factors and severity of a factor as well.