Does mental work consume calories?

Mental work does not significantly increase energy consumption, no matter what kind of mental training you are undergoing. Those who try to lose weight by increasing their brain power should stop trying. To lose weight, use the right method to consume calories. When you see people preparing for exams losing weight rapidly, it’s because they have disrupted the body’s energy balance mechanism, not because of heavy mental work.

There are often people who do not know the difference between grains and are lazy and discuss with me that the food recommended in the "Dietary Pagoda for Chinese Residents 2007" is too much and they cannot finish it, etc. The food amounts recommended in the "Chinese Dietary Pagoda 2007" are suitable for people with a certain level of physical activity (average level). Unfortunately, a considerable number of people do not reach average levels of physical activity, especially those who spend most of their work time sitting or standing and do not engage in physical exercise in their spare time.

The most typical among them are the so-called mental workers, such as teachers, doctors, finance, IT, white-collar workers, clerks, office staff, etc. They consume significantly less energy than average, so they should eat less.

Although the brain weighs little (accounting for 2.5% of body weight), a large amount (15%) of blood enters the brain when it is at rest, indicating that the metabolic level of brain tissue is very high. It has been determined that, in a quiet state, the brain consumes 20 times the amount of oxygen consumed by the same weight of muscle. All this shows that the brain does consume more energy.

However, if you conclude from this that mental work consumes a lot of energy, you would be wrong. Because, according to measurements, even when mental activity is more active, the level of glucose metabolism in the brain is basically the same as when sleeping. When you are calmly thinking about a problem (such as taking an exam), the increase in brain heat production generally does not exceed 4%. It can be seen that during general mental activities, the brain's own energy metabolism rate does not increase significantly. Mental work consumes very little energy, which is incomparable to physical work. In terms of energy expenditure, mental work cannot be considered "work" at all.

However, when the mind is in a highly tense state, such as being upset (very irritable), fearful (trembling with fear) or mentally excited (highly excited or sad and crying), energy metabolism can increase significantly. There are two possible mechanisms. One is that mental tension leads to muscle tension (the most typical example is a novice driver on the road, who is so nervous that he tightly grasps the steering wheel with both hands, and many people lose a lot of weight because of this), which significantly increases energy consumption. Second, when one is mentally excited, the secretion of hormones such as adrenaline and thyroid hormone increases, which accelerates the body's metabolism and increases energy consumption.