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.

Many people tell me I need to lift weights to lose weight.

On mornings when I actually put in real effort, I pay for it with a significant cognitive performance penalty for the remainder of the day. I want to do nothing more than sleep an hour after a workout, which is bad timing, because that's when I need to clock into work.

I stay hydrated, get enough sleep, etc. People tell me that I'm over training, which is ridiculous, because anything less would be easy and contravene the purpose of the workout.

This is why I prefer to exercise in the evening, but there are known negative effects [0] of physical exertion on sleep quality.

If I actually did all the exercise I needed to do at the gym in the morning, then I'd probably have to sleep at 9:00 PM and wake up at 4:00 AM. There's no room to live in that schedule.

[0] https://dx.doi.org/10.1038/s41467-025-58271-x

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...

[2]: https://biomedeng.jmir.org/2024/1/e59459

You don't suffer from a lack of time, but rather a lack of energy. And actually, you don't suffer from a lack of energy, but a lack of activation energy.

We colloquially refer to activation energy as motivation. But maybe that's not the whole story. Some of it is willpower and personality, but maybe some of it is a buildup of adenosine.

This squares with my personal experience. It's harder to start things after day's worth of intense mental effort.

It takes at least a week until it gets stored in the brain if you start taking it.

https://www.science.org/content/article/mentally-exhausted-s...

For me as N=1, training after thinking is easier than the reverse.

Found myself practically stop longing for sweets during programming; have more energy during workouts (135 KG bench press and all the other stuff).

5 g daily is what considered to saturate your muscles.

Some report that any additional helps cognitive tasks (but I haven’t seen definitive studies besides the sleep deprivation).

I take 7.5 g

Willpower is limited. Hard workout means intense cognitive effort is much harder to pull off.