I'd venture to guess you are exaggerating about the 10 liquor stores and fast food joints within a single mile radius because the land would not really allow for that given parking lot spaces and what not, but that is besides the point.
I see what you are saying but at the same time nobody forces people to eat fast food, it is cheap and it is easy to obtain, that is why it is there. It is both a positive and a negative, take those away and some people may not eat...keep them there and health declines. Just the way it is, from a marketing stand point the corps don't care, they are making money by taking money from already poor people, from the people's stand point: they are fine with it, they get a cheap meal that keeps their's and their child's stomachs full.
as for the liquor stores...alcohol is bad for everyone...anyone can become an alcoholic, those stores are placed strategically just like any other place
I don't see you bitching about the abundance of liquor stores in college cities across america so I'll leave that one alone