Does Thinking Burn Calories? Does using extra brain power at work burn more energy?
“The basic answer is yes,” says Ewan McNay, an associate professor of psychology and behavioral neuroscience at the University of Albany. In his research, McNay clearly explains how the brain uses energy to function.
The laws of physics still apply to the brain as an energy system. No work can be done without energy. According to McNay, the brain is the only organ in the body that works solely on glucose, and demanding cognitive tasks require more glucose than easy ones. The areas of your brain involved in memory formation will start using more energy when trying to memorize something challenging. More calories will be burned by doing arithmetic problems than by scrolling through Instagram.
“You will use more energy while engaged in a demanding cognitive task than watching a tv show,” he says. He continues that the difference in calorie burn from one mental work to another is negligible compared to the normal person’s overall energy expenditure.”
Even if the brain uses a lot of energy, challenging mental work only slightly alters brain activity: “maybe a 5% change against the backdrop of all brain activity,” he says.
“This 5% change wouldn’t amount to much, even if you spent the entire day immersed in challenging mental tasks. Calorie-wise it would be quite small. You would need more energy pacing back and forth,” said Dr. Marcus Raichle, a distinguished professor of medicine at Washington University School of Medicine in St. Louis. “As an energy consumer, the brain is the most expensive organ we carry around with us,” he says.
The bulk of your brain’s energy is used to maintain alertness, keep an eye on your surroundings for crucial information, and handle other “intrinsic” tasks.
“A single thought is inexpensive in terms of energy requirements, but the machinery that makes it cheap is costly,” he adds.
He discovered that the brain only makes up 2 percent of the body’s weight, yet it uses 20 percent of humans’ daily energy. The concept that thinking more complex causes the body to burn more glucose is supported by even older research.
In a famous North Umbria University research from 2001, half of the test subjects worked through challenging
verbal and mathematical puzzles while the other half mindlessly pressed a key on repeat. As a possible outcome of higher energy expenditure, those completing the verbal activities displayed a considerable decline in blood glucose levels.
The study concludes that “a period of intense cognitive thinking leads to a detectable decline in levels of peripherally measured blood glucose, which may be connected to higher cerebral energy consumption.”
The way the brain uses energy can vary slightly depending on mental states and tasks. Dr. Marcus Raichle claims that if your brain were to undergo a scan while watching television or working on a crossword puzzle, the activity would change, and your brain would use more energy.
The brain’s capacity to focus would start to decline even during hypothetical instrument-learning sessions as its glucose stores dwindle. You would experience a depletion effect and be unable to maintain the same level of cognitive performance. Refilling your glucose reserves and boosting your brain with some Gatorade or jelly beans could help. However, the calories in those items would significantly exceed that you would burn.
McNay agrees that thinking things through is worth it. There may still be a calorie-burning benefit for those who spend their days doing mentally demanding tasks. Even if you’re only burning a small number of calories every day, that adds to something significant over 50 or 60 years.
