Eats Like a Bird

"He or she eats like a bird," I've heard often said, regarding people who eat little when they are fed. Birds eat an average of 1/4 to 1/2 of their weight everyday, so if humans were to eat the very same way, one who eats like a bird, one can safely speculate, would be very obese, vastly overweight, and would literally eat themselves to an early death at any rate.