Estimates are that the brain uses about 20-25 percent of the body’s total fuel consumption (even though the brain is about two percent of your total weight). What does it use this energy for, what does it do with it? According to Matthew Edlund, MD, in The Power of Rest, “most of the time and energy the brain uses is spent “talking to itself.” He references work by Neuroscientist Marcus Raichle, reported in an article in Science magazine (“The Brain’s Dark Energy”). He used the metaphor of dark energy because so much of what the brain does is unknown. In fact, Dr. Raichle estimates that between 60-80 percent of the brain’s total energy consumption is used communicating between individual neurons and their support cells. It would be fascinating to know exactly what they are saying to each other.