It’s a more sustainable way of living. You only eat what can be produced within 100 miles of where you live. A couple in Vancouver are writing a series of articles about their experience and will soon be publishing a book about it.
http://www.thetyee.ca/Life/2005/12/02/Grain100MileDiet/
I plan to start in January, reducing my consumption of the amount of food that’s not produced domestically. This sort of thing really should be initiated near the first major harvest period, as the winter months need some forward planning, canning, drying, freezing, etc. I only know of about 5-10 foods that are available in January. Meat isn’t an option.
