Answer:
Only two backbones and thousands of ribs.
The more you take, the more you leave behind.
Dies half its life. Lives the rest. Dances without music. Breathes without breath.
This is in a realm of true and in a realm false, but you experience me as you turn and toss.
It is a sound of empty, speak and it'll talk back plenty. But all the more you yack, you'll get the same words back.
You use it between your head and your toes, the more it works the thinner it grows.
Difficult
Animal
Easy
Food
Funny
Kids
Logic
What am I?