The brain makes up 2% of a person's weight. Despite this, even at rest, the brain consumes 20% of the body's energy. The brain consumes energy at 10 times the rate of the rest of the body per gram of tissue. The average power consumption of a typical adult is 100 Watts and the brain consumes 20% of this making the power of the brain 20 W.

Based on a 2400 calorie diet 

2400 "food calorie" = 2400 kcal

2400 kcal/24 hr = 100 kcal/hr 

                          = 27.8 cal/sec 

                          = 116.38 J/s 

                           = 116 W
20% x 116 W = 23.3 W

Glucose is the main energy source for the brain. As the size and complexity of the brain increases, energy requirements increase.

The human brain is one of the most energy hungry organs in the body thereby increasing its vulnerability. If the energy supply is cut off for 10 minutes, there is permanent brain damage. There is no other organ nearly as sensitive to changes in its energy supply.

In 1955, Albert Einstein's brain was preserved for research. Three scientific papers have been published examining the features of Einstein's brain. Albert Einstein's brain differed to normal men's brain in that his brain had more glial cells per neuron that might indicate that neurons in Einstein's brain had an increased "metabolic need"-- they needed and used more energy. Einstein's brain weighed only 1,230 grams, which is less than the average adult male brain (about 1,400 grams). The thickness of Einstein's cerebral cortex was thinner. However, the density of neurons in Einstein's brain was greater. In other words, Einstein was able to pack more neurons in a given area of cortex.

The most recent study concerning Einstein's brain was published in the British medical journal The Lancet, on June 19, 1999. They found that a portion of the brain that governs mathematical abilities and spatial reasoning -- 2 key ingredients to the sort of thinking Einstein did best -- was 15% wider than average allowing better connection between its cells, which could have allowed them to work together more efficiently.

Over the past few years, scientists, in a variety of ways, have tried to get a super computer to mimic the complexity and raw processing power of the human brain. According to biologists, the human brain has approximately 90 billion nerve cells which are linked together by, quite literally, trillions of connections called synapses. Taken together, this system of elaborate connections within the brain provides “hundreds of trillions of different pathways that brain signals travel through."

In an effort to mimic this digitally, scientists a few years ago needed more than 82,000 processors running on one of the world’s fastest supercomputers to mimic just 1 second of a normal human’s brain activity.

More recently, a research study found that the human brain can hold 10 times as much information as previously thought. All told, scientists now believe that the capacity of the human brain is about a petabyte.