I learned this from Interloper, where starvation is the only meal for that game mode. Starving is actually one of the slowest ways to die in the game, and it is possible to starve the whole day and not be at to low condition. If you are struggling with food, you only need 5 cattail stalks per day right before you go to bed to regain just enough condition to break even. You had better not be dehydrated though, because that double condition hit can kill you. (May need a few more stalks if you're going to be sleeping for 12 hours instead of Interlopers 10 hours.)