The average human brain weights about 3 pounds, but researches from University College London have shown that a 3 pound human brain burns almost 20 times as many calories as 3 pounds of muscle. The brain also needs a constant supply of oxygen and food to keep running. 20%-25% of the calories you consume in a day are used to fuel the brain, and for a newborn infant, whose brain is relatively large for its size and growing fast, it can be up to 87%.

The average male uses about 1,500 Calories/day so the average brain will use 300-375 calories per day. This is a huge amount of calories compared to the brains total mass. Brain cells require a lot of nutrients because they are constantly in a metabolic state.