Answer:
My life can be measured in hours, I serve by being devoured. Thin, I am quick. Fat, I am slow. Wind is my foe.
It cannot be seen, it weighs nothing, but when put into a barrel, it makes it lighter.
Almost everyone needs it, asks for it, gives it. But almost nobody takes it.
Some try to hide, some try to cheat. But time will show, we always will meet. Try as you might, to guess my name. I promise you'll know, when you I do claim.
Big as a biscuit, deep as a cup, but even a river can’t fill it up. What is it?
I start with T end with T and within me is T.
Difficult
Animal
Easy
Food
Funny
Kids
Logic
What am I?