. . . If the chocolate bar at the corner store costs $5 instead of $2, less people will buy it, less often. I think that would be a good outcome. These foods used to considered 'treats'.
On my income, or rather on what's left over for me, they are still treats.
Which brings us to the point that such pricing unfairly hits the low income earner, and is going to make no difference to a rich person who is also obese. The way ahead would be to ban the fast food outlets but as that is clearly impractical, if not impossible (it's politically impossible !), then changing the type of food offered along with education seems to me to be the best option, Already some of the FF joints are offering healthier alternatives as are school tuck-shops.
"Get 'em young an' yer've get 'em" could be the slogan of the Food Reformers.