Now the brain, all on its own, burns only about a tenth of a calorie per minute. Percentage-wise, that’s very high for a resting body tissue. When the brain kicks into gear, though, it really gets impressive. When actively thinking about things, the brain can kick it up to burning a calorie and a half per minute. Considering it’s an inert mass of goo that makes up only two percent of a person’s body weight, that’s impressive.
What’s more impressive, though, is a team of scientists found a way to measure when, and how much, a person’s brain is thinking. Neurons work by producing and giving off neurotransmitters. These are chemicals that are produced and given off by one neuron. The next neuron takes up the transmitter, and through these signals get past through the nervous system. In order to produce and transmit these transmitters, neurons suck up twenty-five percent, sometimes more, of the total body glucose, and then twenty percent of oxygen from the bloodstream. It gets the sugar in the form of glucose. During a PET scan, people can see the rate of glucose uptake of different parts of the brain. The frontal lobe is what really needs to be engaged while someone is thinking.
Unfortunately, it can’t be engaged all the time. While a brain takes up about twenty percent, or 300, of a resting body’s 1300 calories a day, and while it has the potential to burn more, it’s estimated that most actual thinking only changes the amount of calories that the brain burns by around twenty to fifty calories per day. That tells us a few things about how much time we spend thinking. Given the shape we stay in today, though, we probably won’t think too hard about that.