Thinking hard burns almost no calories but destroys your next workout • Hacker News Board

Re: Thinking hard burns almost no calories but destroys your next workout

#111

Post by Nevermark » Tue, Feb 17, 2026, 1:31 PM UTC

helsinkiandrew wrote: post #105

sdfhbdf wrote: post #83

Earlier quoted context omitted.

> Can you expand on that please? Because I can tell you as a matter of fact that when I go for a run for an hour I burn well over 800 calories Sure - how did you arrive at the 800 kcal figure? Most likely a wearable or an app, and those estimates are based on rough linear regressions from weight, age, sex, and heart rate - not actual calorimetry. The error margins on those numbers are significant, but the devices pre…

> That's what I mean by "myth" - not that exercise burns zero calories, but that the popular mental model of "I ran for an hour so I earned X calories of food" is built on inaccurate measurements Over the last few of decades there's been a lot of lab research calculating the gross efficiency of the human body with different factors (size, sex, fitness etc) and I think these estimates that sports apps give are very cl…

To the degree the body diverts any housekeeping or thermogenic calories to exercise calories, which from basic biological adaptivity and thermogenic control must be true at some level, that math will be misleading.

Not that doing x work doesn’t burn y energy, but that +x work in exercise does not burn +y energy at the end of the day.

Exercise is an alternate heat source, approximately 1-to-1 with thermogenic heat (albeit, not distributed as evenly). So much so that our body has to switch to cooling strategies.

And the body can respond to exercise expenditures by reducing other expenditures and using calories more parsimoniously in other dimensions.

It is interesting that during periods in which I have a habit of daily low intensity exercise, I feel like I have more energy than periods I don’t do any exercise, even if my calorie intake is the same.

Another noticeable effect is any allergies from local plant life I get clear up quickly during and after exercise. My immune system runs a tighter, less reactive ship.

Those baseline calories are not just often underestimated in a static sense, but are also dynamically adaptable.

One reason may be is that we evolved to burn far more overt calories through a day than our extra-exercise day burns. Our body has mechanisms for storing surpluses but almost certainly raises baseline use as well. Which is easily diverted back to exercise.

On the other hand, beyond any net expenditure from regular lifting weights (as work), to the degree greater muscle mass is achieved and maintained, weight lifting directly raises the body’s baseline expenditures.

Re: Thinking hard burns almost no calories but destroys your next workout

#112

Post by evanjrowley » Tue, Feb 17, 2026, 1:34 PM UTC

Balancing health while being productive as an average adult seems like an impossible equation today.

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

Re: Thinking hard burns almost no calories but destroys your next workout

#113

Post by xiphias2 » Tue, Feb 17, 2026, 1:44 PM UTC

evanjrowley wrote: post #112

Balancing health while being productive as an average adult seems like an impossible equation today. 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 i…

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

This is stupid. All you need to do is to get used to being hungry to the point of losing 0.1kg/day and measure yourself a lot (I'm doing the same).

Actually for me working out increases my appetite, and I feel like I have to eat so thar the gym session doesn't go wasted.

Re: Thinking hard burns almost no calories but destroys your next workout

#114

Post by tsimionescu » Tue, Feb 17, 2026, 1:45 PM UTC

topocite wrote: post #101

sdfhbdf wrote: post #87

Earlier quoted context omitted.

This is well-intentioned but I think it oversimplifies in ways that can actually be harmful. "Just get used to being hungry" is rough advice to give people - chronic hunger is one of the main reasons diets fail, and framing weight loss as a willpower contest against hunger ignores that satiety is heavily influenced by _what_ you eat, not just how much. A 400 kcal meal of protein, fat, and fiber will keep you full for…

No, the common "wisdom" you are puppeting here is harmful because it just doesn't work. We have been telling people for decades now to be worried that they might harm themselves by too much restriction and it is just wrong. What is harmful is being over weight. What is harmful is then confusing people that they are somehow going to lose weight without much restriction or being hungry. This also scales really bad with…

I think the advice that everyone who is overweight or obese really needs is to experiment with different ways of reducing their food consumption while managing their hunger and cravings, and find out a method that works for them. I don't think there's any universal solution. Even saying "eat less simple carbs, those make you more hungry because of this and that chemical pathway" is not good universal advice, because food consumption is not strictly tied to hunger in all people. It is up to you as the one who wants to lose weight to experiment and figure out what motivates you and works for you longer term.

For example, I don't feel satisfied with my meal if I don't feel slightly full. So, what has worked for me is to generally have a single large meal per day, in which I will typically eat whatever I've been really craving since my last meal. In some days that might be steak and brocolli, in other days it might be a McDonald's meal, or some cake. When I get cravings, it's far easier for me to defer them to tomorrow's meal than it would be to just stop eating junk food entirely, or to eat half a burger and two fries from the bag. The exact opposite might be true for other people, and you won't really know until you've tried for yourself.

One thing I will note - I think one of the concerns of the poster you are replying to with focusing too much on enduring hunger is that it might lead some people to develop anorexia, which is indeed a huge problem, even when the person is really overweight (since their anorexia will not just go away once they've lost that extra weight, it will keep going until they get dangerously malnourished).

Re: Thinking hard burns almost no calories but destroys your next workout

#115

Post by ChoGGi » Tue, Feb 17, 2026, 1:52 PM UTC

evanjrowley wrote: post #112

Balancing health while being productive as an average adult seems like an impossible equation today. 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 i…

> Regardless of strain, exercise bouts ending ≥4 hours before sleep onset are not associated with changes in sleep.

Exercise a little earlier in the evening?

Re: Thinking hard burns almost no calories but destroys your next workout

#116

Post by MagicMoonlight » Tue, Feb 17, 2026, 2:12 PM UTC

I’ve noticed this. Both physically tiring and mentally tiring activity seem to deplete the same pool.

Re: Thinking hard burns almost no calories but destroys your next workout

#117

Post by PleasureBot » Tue, Feb 17, 2026, 2:14 PM UTC

sva_ wrote: post #68

sdfhbdf wrote: post #15

I'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 beginni…

> debunk the popular myth for my friends that exercise burns a lot of calories Depends on your level of exercise. I often cycle 100km per day and can tell you if I ate only the 2000 kcal I hypothetically need I would go into a strong deficit.

There's been metabolic studies that show that this isn't true. Comparisons of total caloric usage of completely sedentary people and people who have high exercise load are indistinguishable. There is a large difference among individuals, but not correlated to exercise levels. Sedentary people who start training hard will have a spike in caloric usage for a few months, but their body adapts and calorie burn returns to the same level that it was when they were sedentary. This was new research, so there wasn't an explanation for it. The authors hypothesized that it could be that the body reduces caloric spend on other things, like stress responses, when it is adapted to high exercise levels/ They did note that some extremely elite athletes can temporarily increase their caloric burn (think Michael Phelps eating 10k calories per at some points when training for the Olympics) but its not something most people can achieve or sustain.

Re: Thinking hard burns almost no calories but destroys your next workout

#118

Post by soared » Tue, Feb 17, 2026, 2:17 PM UTC

evanjrowley wrote: post #112

Balancing health while being productive as an average adult seems like an impossible equation today. 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 i…

Hate to be the bearer of bad news, but you are likely over training. Check out heart rate zones, optimal workouts for weight loss/muscle gain. IE for endurance sports most of your training time should be zone 2, which if casually “a level of breathing where you could have a conversation”. So not breathing hard. It’s counterintuitive, but you should do workouts pretty close to easy.

Re: Thinking hard burns almost no calories but destroys your next workout

#119

Post by soared » Tue, Feb 17, 2026, 2:21 PM UTC

PleasureBot wrote: post #117

sva_ wrote: post #68

Earlier quoted context omitted.

> debunk the popular myth for my friends that exercise burns a lot of calories Depends on your level of exercise. I often cycle 100km per day and can tell you if I ate only the 2000 kcal I hypothetically need I would go into a strong deficit.

There's been metabolic studies that show that this isn't true. Comparisons of total caloric usage of completely sedentary people and people who have high exercise load are indistinguishable. There is a large difference among individuals, but not correlated to exercise levels. Sedentary people who start training hard will have a spike in caloric usage for a few months, but their body adapts and calorie burn returns to…

Absolute nonsense. The claim is that if I produce 2.5watts per kg in body weight for 2 hours, I’m not going to burn any extra calories? So when I “bonk” and exhaust glycogen stores due to underfueling that’s actually not true?

Re: Thinking hard burns almost no calories but destroys your next workout

#120

Post by diogenes_atx » Tue, Feb 17, 2026, 2:22 PM UTC

evanjrowley wrote: post #112

Balancing health while being productive as an average adult seems like an impossible equation today. 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 i…

Something else you might try is changing your diet. After I became a vegetarian and eliminated refined sugar and excess sodium from my food, my health improved, as well as my sleep. I am no longer pre-diabetic. And the food that I eat is wonderful, many different ways of preparing beans and lentils for protein instead of meat.