How often do you hear that so-and-so eats like a bird? "How does he survive on that little food? I'd pass out!" Well, the truth of the matter is birds eat like pigs. Many birds eat as much as twice their weight in a day. That means that a 150-pound person would have to eat 300 pounds of food in a day. So next time you want to compliment a person's eating habits, say that they eat like a pig (which eats less than a bird).