This is not my idea but one that I ponder as a good idea. There is more information at http://en.wikipedia.org/wiki/Local_food

I think for most it will focus your diet on healthy food because most manufactured food is not within 100 miles, but whole foods are grown within 100 miles and then you are forced to create meals with whole foods.

I am sure there is an economy of scale issue such that it is actually more efficient to buy foods grown further away and have been distributed, I'll have to look into that. My intuition says that it probably is the case, but supporting local food growers will change that because with their growth they will become more efficient.