The brain, an energy glutton

Your brain is barely 2% of your body, yet it burns close to a fifth of all the energy you spend in a day. It is never not hungry.

Much of that expense goes not to solving maths problems or making big decisions, but to keeping neurons ready to fire and rewiring their connections. The brain is working hard even when you think you're resting.

That energy bill is one reason researchers study why heavy thinking really does tire you out: keeping billions of neurons active is costly, even if you never move a muscle.

Source: Scientific American