People make jokes about how it hurts to think, or that it's so exhausting sometimes it's just not worth it, and although we all laugh it turns out there may actually be some truth to those comments! Thinking too hard can actually make you tired.

It all comes down to the fact that our brains need glucose to work, and that when we concentrate we use up glucose faster than when we don't. And the older you are (keep in mind this was done with rats so take it with a grain of salt) the longer your glucose levels take to bounce back up to normal.

So now you can say how tired you are from thinking all day, and when people laugh just look at them, "I'm serious, man."