The human brain is one of the most complex organs in our body and requires a significant amount of energy to function properly. In fact, it accounts for about 20 percent of our total energy requirements, or an average of 400-500 calories per day. However, the amount of energy needed varies depending on how hard the brain is working.
Even under deep anesthesia, the brain still requires about 150 calories per day. Experiments with rats have shown that simply transitioning from a deeply anesthetized state to a conscious but anesthetized state increases energy demands by 50 percent. When we are awake, a significant portion of brain function is used for controlling muscles and processing sensory input.
Research has also shown that the brain's metabolic requirements depend on an individual's IQ when it comes to abstract problem-solving. Those with higher IQs expend more energy on a problem that is subjectively challenging for them.
Unlike any other part of the body, the brain runs exclusively on glucose, which is the sugar that fuels our body's energy. Strenuous cognitive activities require more glucose than simple ones. During a difficult memorization task, the parts of your brain involved in memory formation will start consuming more energy, while other brain areas will show no such increase.
While it's true that intense cognitive tasks burn more energy than simply watching television, the difference in calorie burn is relatively small compared to our overall energy expenditure.
Find out how much energy your brain consume using our Brain Energy Consumption calculator