Cold Turkey?

When one is addicted to a substance, it's often suggested that going "cold turkey," i.e. suddenly and completely abstaining from it, is a good way to go.

...but if what you're addicted to is food?

All I can do is try to avoid fast food, which should be a great improvement. But where do I draw the line? No Burger King or McDonalds is clear enough. But what about Subway sandwiches? What about the BBQ pork sandwiches at the cafeteria where I work? Do I just go with foods I cook myself? That's not practical, unfortunately. I know from a painful few weeks in college that I'm not wired for vegetarianism. So what's the cut-off from "Bad Food" to "Good Food?"