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.
I fly through the air on small feathered wings, seeking out life and destroying all things.
Pregnant every time you see her, yet she never will give birth.
It's got twists and turns, but has no curves. Twist it to fix it, turn it to ruin it. What is it?
This only turns over once you have traveled very far. What is it?
What do you purposefully put lots of in and on your body, but run away from when you encounter it outside?