Is anyone here able to offer an explanation for why our brains are able to do really complex tasks without using much energy, at least compared to AI systems?
Thinking hard burns almost no calories but destroys your next workout
11–20 of 151 posts
Re: Thinking hard burns almost no calories but destroys your next workout
#12Was expecting the article to mention creatine which interacts with ATP. It's a supplement that's so well studied that almost everyone should take it, even if you don't workout at all. In my experience it has helped tremendously with mental endurance (n=1 but there are some studies that support it, especially in older people with cognitive decline).
Creatine ruins my sleep
Find myself getting up multiple times a night to pee.
Even once is rare unless I've been out drinking for the night.
Re: Thinking hard burns almost no calories but destroys your next workout
#13Is anyone here able to offer an explanation for why our brains are able to do really complex tasks without using much energy, at least compared to AI systems?
Completely different architectures and mechanisms. Machine learning draws inspiration from some biology concepts, but implements it in different way.
Re: Thinking hard burns almost no calories but destroys your next workout
#14Is anyone here able to offer an explanation for why our brains are able to do really complex tasks without using much energy, at least compared to AI systems?
If I'm not in flow state focusing on some programming problem, my brain is still going a million miles a minute pontificating about 10 different threads of nonsense at once. So I could see where focusing on one task doesn't actually burn any more energy, it just pulls in all those other workers and puts them to work on one thing.
Re: Thinking hard burns almost no calories but destroys your next workout
#15I've also been interested for some time in how metabolism works and wanted to debunk the popular myth for my friends that exercise burns a lot of calories, since I was under the impression that around 80% of energy we burn is just by "living" - breathing and thinking.
Reading this article I'm a little confused by the author's conflation of brain energy and the energy expenditure of the body as a whole. In the beginning they mention:
> "Your brain consumes roughly 20 to 25% of your body's total energy at rest"
while later they say:
> "Even chess grandmasters, who sit for hours in states of intense concentration, burn only about 1.67 calories per minute while playing, compared to 1.53 calories per minute at rest"
That second figure seems to refer to whole-body expenditure, not just the brain. And intense cognitive work doesn't happen in a metabolic vacuum - there's increased cerebral blood flow, elevated sympathetic nervous system activity, changes in heart rate variability, hormonal shifts (cortisol, adrenaline). These all have systemic metabolic costs that go beyond the glucose the neurons themselves consume. So the "it's just a banana and a half" framing might be undercounting by quietly switching between brain-only and whole-body measurements.
Also somewhat related - the link to businessinsider about chess grandmasters is broken, but another very interesting rabbit hole here is how energy expenditure is actually measured. A lot of what consumer devices and even many studies report is based on proxy biomarkers like heart rate, HRV, weight, age, and sex, run through linear regression models. True calorimetry (indirect via gas exchange, or direct in a metabolic chamber) is expensive and impractical outside lab settings. That means the precise calorie figures cited with such confidence - the "100 to 200 extra calories" from a day of thinking, or the per-minute burn rates of chess grandmasters - likely carry wider error bars than the article suggests. We don't really have a great way to measure real-world energy expenditure accurately at the individual level, which makes me a bit cautious about the neat narrative of "thinking is calorically cheap, full stop."
That said, the core point about adenosine accumulation and perceived exertion affecting training quality is fascinating and well-supported — that part of the article is genuinely useful regardless of the calorie accounting.
Re: Thinking hard burns almost no calories but destroys your next workout
#16Is anyone here able to offer an explanation for why our brains are able to do really complex tasks without using much energy, at least compared to AI systems?
The brain relies on discrete, sparse events in space and time to handle computation.
Most of the computation and learning that occurs is attributable to the relative timing of spiking events. A lot of information can be encoded in the delay between 2 spikes. The advantage of biology is that there is no explicit quantization of the time domain that must occur. Biology gets to do a lot of things "for free". Simulating causality in a computer in a similar way requires a priority queue and runs like ass by comparison.
Re: Thinking hard burns almost no calories but destroys your next workout
#17The product that this article is advertising seems to be pretty inaccurate and their marketing seems to be burying that information.
The big copy on the front page says:
> Your Apple Watch *tracks* VO2 Max—one...
While you have to read through FAQ where you see:
> The watch *estimates* your cardio fitness during outdoor activities and stores it in Apple Health, which our app reads automatically.
All emphasis are mine.
I think it's a little disingenuous to sell this as "Your VO2 Max, finally visible" when it's actually just an estimate from a watch, based on biomarkers. When the real VO2 is measured in a lab with a more involved equipment.
A 2025 validation study involving 30 participants found that Apple Watch underestimated VO2 max by a mean of 6.07 mL/kg/min (95% CI 3.77–8.38) when compared to indirect calorimetry, the gold standard method. The mean absolute percentage error (MAPE) was 13.31%, and the limits of agreement showed considerable variability ranging from -6.11 to 18.26 mL/kg/min [1]. Another 2024 study found similar results, with the Apple Watch Series 7 showing a MAPE of 15.79% and poor reliability (ICC = 0.47) [2].
[1]: https://journals.plos.org/plosone/article?id=10.1371%2Fjourn...
Re: Thinking hard burns almost no calories but destroys your next workout
#18Shouldn't the chemistry hide the usage of calories by the brain? It gets basically a supply run at night - when its washed with lymph, sugar supplied and then subsists on that for new memory formation and computation with small scale supplies delivered during the day via the blood stream? So a hard thinking experience should show up downstream as calorie usage during the following sleep?
Re: Thinking hard burns almost no calories but destroys your next workout
#19Was expecting the article to mention creatine which interacts with ATP. It's a supplement that's so well studied that almost everyone should take it, even if you don't workout at all. In my experience it has helped tremendously with mental endurance (n=1 but there are some studies that support it, especially in older people with cognitive decline).
Creatine ruins my sleep Find myself getting up multiple times a night to pee. Even once is rare unless I've been out drinking for the night.
That's interesting. I'm having the same problem. I usually have it after my workout in the evening. Should I try moving it to earlier in the day?
Re: Thinking hard burns almost no calories but destroys your next workout
#20Was expecting the article to mention creatine which interacts with ATP. It's a supplement that's so well studied that almost everyone should take it, even if you don't workout at all. In my experience it has helped tremendously with mental endurance (n=1 but there are some studies that support it, especially in older people with cognitive decline).
How much are you taking?
Second anecdote, I take between 10 and 15 grams. I don’t experience cognitive effects at lower doses (though my weightlifting endurance is still higher on lower doses). I also don’t eat meat so don’t have any incidental consumption