I hear this a lot from ill informed vegetarian wannabes. Meat rots in your colon for days, some even claim months and some, the really whacky ones who won’t even eat dairy and claim tofu will cure cancer tell us it sits there FOREVER!! Well, I just wanted to share this fact with you. What rots in your body is beans, grains and vegetables, not meat. In fact, the meat is long gone before any issues with undigested matter pass into your intestines and start to decompose.
(Also take a look at this: Paleo in 6 easy steps)