Why can’t we burn more or less calories by working our brain when it already uses a fifth of our daily energy usage?

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Hello,

So my question is, our body uses a certain amount of energy through the day and 20% of that is used exclusively by the brain.

Why can’t we increase or decrease the calorie usage of our minds to burn more or less calories?

My own theory is that the brain runs on a base threshold of energy and it normally is around 20% but it doesn’t explain why doing brain teasers/puzzles doesn’t increase it.

And bonus if you can explain how doing extremely challenging problems for any amount of time makes you feel physically tired (such as taking a test).

Edit: there have been a amazing amount of answers while I was asleep (posted this before sleeping for a solid 10 hours), my questions about the brain functionality has been answered

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21 Answers

Anonymous 0 Comments

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Anonymous 0 Comments

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Anonymous 0 Comments

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Anonymous 0 Comments

It’s because “conscious thought” is only a small part of what your brain actually does and therefore a small part of its energy expenditure. Increasing the intensity and duration of conscious thought is only slightly increasing the work that your brain is doing.

Your brain, through the nervous system, also regulates the majority of your body functions, including your enzyme and hormone systems. So if you want to fire your brain right up you need to not only think more but feel more and do more stuff.

If you want to increase your brain’s work rate across most of its functions, and hence achieve a higher energy burn, you can. But the methods are normally not things you should do flippantly, for example taking certain drugs or getting into very stressful situations.

Even if you’re able to achieve safe conditions, it’s not a good idea to do this a lot. Your brain, like any other organ, wears out. There’s a reason it’s evolved to be very efficient at what it does.

Edit: a lot of people talking about chess because of an ESPN article. Chess players don’t burn 6000 additional calories playing chess. There was a great reply below from u/avocadokadabra that referenced another Reddit thread where this was debunked: [you can find it here.](https://www.reddit.com/r/chess/comments/s0tqcd/chess_grandmasters_do_not_burn_6000_calories_a_day/?utm_source=share&utm_medium=ios_app&utm_name=iossmf)

I’d also like to add that in my comment I explicitly separate “conscious thought” from subsequent physiological effects, although they may be _related_ to conscious thought. In the example of the chess games, it’s clear (even in the often misquoted ESPN article) that the majority of the additional energy burn is not happening in the brain, it’s happening in the rest of the body as a result of elevated blood pressure, excessive breathing, and it’s certainly not due to conscious thought, it’s the systemic effects of being in a hyper-stressful situation.

I’m so glad this generated a lot of conversation! 🙂

Anonymous 0 Comments

First off, the math isn’t on our side. the brain uses about 20% of your baseline *resting* energy. If I run for an hour, I’ll burn 1,000 Cal, which bumps my daily usage by more than 50% and the brain usage won’t increase.

If I could somehow double my brain’s energy usage for a full 24 hours – **which I can’t** – that would still only be a 20% increase over my normal baseline. If I did it for an hour (how long my run takes), it would be less than a 1% overall increase over baseline – 1/24th of 20%.

As to *why* I can’t increase the brain’s energy: it’s hardwired into how the brain works. The human brain uses a very consistent amount of energy at all times, about 20 Watts. There are 100 billion neurons in the brain, and if you increase activity (i.e. energy consumption) in one brain region, other regions will decrease their average activity to balance the total energy needed. Even if an activity engages 1 billion neurons, the other 99 billion can easily balance out that increased energy with a very small decrease in average activity.

The brain operates separately from the rest of the body in many ways. The blood brain barrier stops a lot of what’s in our bloodstream from reaching the brain. Blood pressure in the cerebrovascular system is even controlled separately from the rest of your body. It’s pretty finely tuned.

Anonymous 0 Comments

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Anonymous 0 Comments

I can pull a full day of hard labor get home and still have energy..but when I have to do 3 or 4 hours of reading for school i feel drained.

Anonymous 0 Comments

Most of the reason your brain exists is for your senses and motor units. Not for what your perception of thought is. The vast majority of real estate is designed for your physical instincts and your drive to seek out food water shelter and romance. To defend itself automatically in danger.

It’s much easier (generally) for a weapon in your face to raise your heart rate and body temperature, than the thought of one. Your wired to react to this stressor with increased physical activity and body temperature.

What you think is thinking can’t stimulate it the same.

Anonymous 0 Comments

Your brain spends most of its time designing and interpreting reality, keeping your body working in the background, being aware and responsive to stimuli. Solving a math problem works your brain harder like drawing the math out in minecraft with minecraft blocks works your computer harder. 99% of the work is the baseline level of work.

Anonymous 0 Comments

You can, but you’ll have really engage your brain in strenuous thought.

https://time.com/5400025/does-thinking-burn-calories/?amp=true

I remember reading another article awhile back on the subject. I think it was about high level Chess tournament that noted how many calories the competitors burned sitting their contemplating their next move and strategies. However, and I can’t emphasize this enough, you have to be engaged in very strenuous thought. You’re not going to burn a relevant amount of calories studying calculus or doing a difficult mental task at work.

Edit:
I believe this was the article.
https://www.espn.com/espn/story/_/id/27593253/why-grandmasters-magnus-carlsen-fabiano-caruana-lose-weight-playing-chess?platform=amp