Even though your brain only makes about less than 3% of your entire body, it takes up a whopping 20% of energy to operate. What is all of this energy used for? Well, a lot of it goes towards the maintenance and production of cell-growth. The remaining energy is used to fuel electrical impulses in the body so that they work better with one another. While size is usually a factor in most cases, it isn’t when it comes to the human brain.