When I eat rotten flesh from a zombie, my health bar turns green, though still seems to increase. I've had people tell me to eat rotten meat quickly to avoid being poisoned, why is this?
Food poisoning does not stack - that is, if you're already poisoned, and then get poisoned again, only one of those poison effects remain. So, if you quickly eat a lot of the stuff, the hunger meter will increase faster than it decreases from the food poisoning.
You'll still get poisoned, but because you gain more points than you lose, the effect of the poisoning is not as severe.