Roughly three weeks. However, after more than a few days you become massively less fit, so if you're thinking of a survival situation always take more food than you will ever need. Assume that you are going to starve the mealtime after you eat your last ration.
Theoretically could a fat person eat their excess flesh and survive on that?

I try to find an article I see in the paper, and it returns 1000s of hits that are in no way related to the terms I search for, but if I type in the exact title, it's "no file found". 
