You can't have it both ways, if stopping candy leads to cigarette money then cigarettes are healthy because anyone who smokes has less money for heroin.
That's not having it both ways. It's the problem with having incomplete data.
But if cigarettes are the thing preventing people from buying heroin with the money you deterred them from using to buy soda, that doesn't mean that the soda money is going someplace better than it was before your law, it only implies that "well then we just need a higher tax on cigarettes" wouldn't be a beneficial solution.
This is literally the thing the person who started this thread is asking for:
> This isn't the right definition of success. The first minimal requirement for this to be a successful initiative is that the community lost weight overall. Or even gained weight, but more slowly than other communities.