While you’re getting your nightly shut-eye, your body is still pretty active, even if you’re not aware of it.

When you’re asleep, your body actually speeds up cell repair and cell growth while your brain processes and discards the useless information you’ve accumulated throughout the day. Not to mention, your body does all these other strange things while you sleep, too.

But do you burn calories during your nightly slumber, and if so, how many? You do, and it might be more than you think: “While the body isn’t burning nearly the amount of calories as it would in motion, it is far from zero,” Bill Fish, co-founder of the sleep-better website Tuck.com, tells RD.com.