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
In: 7004
You want to be just like L am I right?
Much of the heat loss comes from the need to keep your brain at a nice constant temperature, coupled with it being relatively exposed.
Your brain is more like a computer/microprocessor, with a pretty simple set of power-saving modes, so while you might burn a few more calories through mental effort, the heat loss / maintenance of temperature is far more significant.
First it’s important to know that you DON’T only use 10% of your brain at once. That’s a silly myth.
We know that nearly all of the brain is “in-use” almost all of the time that you’re alive (this is a very rough generalization but for eli5 we won’t go into complicated details)
And remember the brain is not a computer, it’s meat
Your muscles are meat too, but the brain is not a muscle, it’s a different kind of meat. Also remember, you have LOTS more muscle-meat than brain-meat.
Thinking really hard does increase the activity in the brain. But the brain is not like your computer, it doesn’t simply need more electricity to go ‘faster’. Your brain uses special chemicals that allow electrical activity instead. Your body cannot simply ‘burn’ calories to make this ‘faster’ or ‘stronger’, it is a very complicated process.
So all the parts of your brain need to keep working constantly so you can stay alive and healthy. The amount of work each is doing at one time can change but overall it stays pretty consistent. When one part needs rest a different part will pick up the slack. When you think very hard some areas become ‘quieter’ and some become more active. Now to your question: can we measure the changing caloric usage of the brain when that happens?
Well the issue is that the body, the rest of your meat as a whole, is *very* responsive to the brain. So when you are thinking very hard the rest of the body WILL burn *significantly* more calories above the resting metabolic rate.
There is no good way to measure exactly how much of that extra usage is just “for” the brain, lot’s of people try to guess but we don’t really know for certain. But we do know that caloric usage is a lot less (about one fifth) than what is used by the rest of the body.
So we can’t really say that the brain is going to burn a lot more calories when thinking hard because even if you do end up using a lot more calories when thinking very hard those calories are mostly burnt from the effect of thinking on the body, not from the thought itself
Think of your body like a car. If you think you turn on the headlights. If you think really hard you turn on the high beams. It won’t use that much extra gas compared to revving the engine. Running would be like driving on a race track.
For the same reason hard drives don’t get heavier when they’re full of meaningful data vs rubbish
It does, it just isn’t enough to matter. Its like idling your car versus idling your car with the radio on. Technically yes your car is using more energy with the radio running, but at the end of the day the difference is so small to the base fuel requirements as to be negligible in all but the most extreme cases.
This thread is freaking me out thinking about squishy stuff in my head is responsible for sooooo much.
And like… I am that squishy stuff. Without your brain, you’re not you. So I’m actually using myself to think about myself…
I’m gonna go smoke another joint…
>Why can’t we increase or decrease the calorie usage of our minds to burn more or less calories?
We can, you probably don’t want to.
https://pubmed.ncbi.nlm.nih.gov/29512224/
>Interestingly, near the termination of prolonged dry static breath holds, recent studies also indicate that reductions in the cerebral oxidative metabolism can occur, probably attributable to the extreme hypercapnia and irrespective of the hypoxaemia.
If you’re under water, the last thing you’ll do is take an involuntary breath.
>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).
Because your brain is both consciously and subconsciously in charge of your body. [Brain training for physical endurance](https://www.runnersworld.com/training/a20795307/brain-endurance-training/) is a thing.
Apologies to any neuroscientists who happen to read this and start foaming at the mouth from my mischaracterization-through-simplification explanations. I can’t quite ELI*5*, but this is the best *ELI’mNotAGradStudentInBiology* I can come up with.
A few points I didn’t see discussed elsewhere:
You only have conscious access to a tiny fraction of your brain. Almost all brain activity, including most “thinking” is done by structures that are opaque to the conscious mind. For example, both your eyes have a large blind spot where the optic nerve attaches to the retina, but the image “you” consciously see has that gap already filled in by some tiny corner of your brain you probably don’t even know exists. That function burns a (probably pretty steady) number of calories and absolutely no amount of conscious exercise of will is going to result in you being able to “turn that off” and see the image that actually registers in your eyes. So not only are the parts of your brain associated with non-conscious activities (breathing, heartbeat, endocrine system, etc.) unable to be controlled or even really affected by your conscious choices, but many parts of your brain associated with things you consciously do (looking, reading, listening, speaking, etc.) are done outside of conscious control. And that god they are! Can you imagine what a nightmare even just talking would be if you had to consciously control your lungs, vocal cords, tongue, etc. not to mention all of the rules of grammar and pronunciation for every single word?
Many people think the brain is like a computer, and they know that power consumption on a computer goes way up the “harder” it works on something. But that wasn’t always the case; back in the day DOS and even early Windows machines drew a steady amount of power no matter what you were doing. If, for example, running full-bore 100% processor utilization programs like something that calculates a million digits of pi took 100W of power for the processor, then just sitting there blinking the cursor would take the same 100W. This is actually a problem you can run into when using virtual machines of old operating systems that are expecting old chips like 8088 and 8086/286.
As to your “bonus,” nobody is certain exactly how mental effort leads to physical exhaustion, but it is generally believed that by burning large amounts of glucose (the simple carbohydrate that your body, especially the brain, uses for power) your brain will make more adenosine. Adenosine (in its triphosphate form, ATP) is a compound that your brain uses during the physical act of thinking, it’s like the raw material that drives the actual electrical impulses that constitute thought. It also blocks the absorption of (or maybe the production of?) dopamine, the hormone that helps you concentrate and, in general, exercise conscious will. With your dopamine depressed literally everything seems to take more and more effort, which your conscious mind interprets as “being tired.” It’s the same reason people with depression disorders lay around and sleep a lot. Assuming you’re normal/healthy, your brain is able to get more glucose fairly quickly, but the “lack of available energy” isn’t what is actually causing the fatigue, your brain’s perception of it performance is.
Your premise is wrong
It uses a fifth of your RESTING energy consumption. When we’re active your muscles consume much more energy than at rest. Similarly when your muscles recover they also consume more energy than normal. It’s those two together that produce the energy drain.
Practicing or neglecting your mental activity has implications for learning capacity and nutritional balance needed but is overall negligible for calories.
Latest Answers