4 ms·

> debunk the popular myth for my friends that exercise burns a lot of calories Can you expand on that please? Because I can tell you as a matter of fact that w

by jahnu 8mo ago

> debunk the popular myth for my friends that exercise burns a lot of calories 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.

nandomrumber 8mo ago
But you’ve never directly measured calorie expenditure while running, so how can you be certain?
nick486 8mo ago
I think it sort of depends on how you look at it. If 800 is an hour of running - that's probably "a lot" for quite a few people. But 800 is also just a sandwich. Which isn't all that much. So if you view this from a time use perspective, just skipping that sandwich is way better than running for an hour. And many people can't spare an hour a day just to make up for a sandwich. Hence - "not a lot" - Its too expensive time-wise for the caloric balance effect it provides. Just skip the sandwich instead.
- BoppreH 8mo ago
  I agree with the general message, but I'm curious what ingredients go in your 800 calorie sandwich. That's more than a double Big Mac with 4 patties (780 kcal)!
  - mriet 8mo ago
    Lots of mayo.. and butter. It's more like a butterich, realistically. ;)
  - asimovDev 8mo ago
    Maybe the Elvis sandwich https://en.wikipedia.org/wiki/Peanut_butter,_banana_and_bacon_sandwich https://en.wikipedia.org/wiki/Peanut_butter,_banana_and_baco...
- jahnu 8mo ago
  That's a big sandwich :) Big Mac = 580 Cal. I'm going to eat lunch one way or another and for me it's going to be under 800. Skipping meals isn't really a good choice, imo, but ok.
  - tsimionescu 8mo ago
    You need to eat roughly somewhere between 1300 and 2000 Cal every day to maintain your weight even if you are doing to exercise at all. If you want to lose weight, it's far easier to remove 800 Cal from your diet, at least time wise, then it is to exercise 800 Cal's worth every day. Either way, if you're losing weight at any appreciable rate, you will feel hungry (at least if it's not chemically induced in some way, such as chemo or GLP-1 inhibitors or similar). That's just something you have to get used to if you want to lose weight.
    - jahnu 8mo ago
      > If you want to lose weight, it's far easier to remove 800 Cal from your diet, at least time wise, then it is to exercise 800 Cal's worth every day. That I absolutely agree with and so do my legs ;) I only found the suggestion that exercise _doesn't_ burn calories a bit weird. > you will feel hungry That I also agree with... all this talk of sandwiches!
      - Izkata 8mo ago
        > I only found the suggestion that exercise _doesn't_ burn calories a bit weird. I mean... No one said that? The very first comment was about how it's not a lot / not as much as people think, not that it's none.
    - sdfhbdf 8mo ago
      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 hours; 400 kcal of simple carbs will leave you hungry again in 45 minutes, in part because of the insulin and blood glucose dynamics involved. The calories in/out model isn't wrong exactly, but it's so reductionist that it becomes misleading in practice. It omits hormonal responses (insulin, leptin, ghrelin), the thermic effect differences between macronutrients (your body burns 20-30% of protein calories just processing them vs 0-5% for fat), gut microbiome composition, sleep quality, stress hormones, meal timing, and individual metabolic variation. Two people eating identical calorie counts can have very different outcomes. Telling someone "just eat less and accept the hunger" without any of that context can set them up for a miserable yo-yo cycle - or worse, a disordered relationship with food.
- xnorswap 8mo ago
  What kind of sandwiches are you eating? 800 calories is a ridiculously large sandwich. Even Tesco's bacon & egg triple is only 550 : https://www.tesco.com/groceries/en-GB/products/260422235 https://www.tesco.com/groceries/en-GB/products/260422235 I'm struggling to find anything I'd describe as a sandwich come close to 800 calories.
  - nick486 8mo ago
    Fair enough, but so is 800cal/h exercise. And I'd rather overestimate the intake.
  - rpdillon 8mo ago
    Footlong Spicy Italian at Subway ($10 sandwich) is 1320 cals. EDIT: the trend holds pretty well at the footlong size (which is a big sandwich). 18/26 sandwiches they offer are >1000 calories.
    - xnorswap 8mo ago
      A foot-long sub is not "just a sandwich", it's a meal for 2. Secondly, I can't see how you can get to 1320 calories for a footlong italian going by this: https://www.subway.com/en-gb/-/media/emea/europe/uk/nutrition/uk-and-roi-nutritional-information-june-2025.pdf https://www.subway.com/en-gb/-/media/emea/europe/uk/nutritio... Even counting footlong bread + footlong Italian Sub it only comes to ~1100. And as it makes clear, a footlong is 2 6" servings, it's disingenuous to pretend that's a sandwich.
      - rpdillon 8mo ago
        I'm talking about what happens in reality, not what the "serving size" is. Gobs of folks order a footlong at Subway and eat it for their meal. As for nitpicking on calories: the Subway site is incredibly tough to navigate. Just use https://subwaymenupedia.com/ https://subwaymenupedia.com/, since averaging across location is really tough. I wish my point were uncontroversial: millions of people buy footlongs that are over 1000 calories as a regular habit. I'm critiquing folks that are incredulous about this. Subway is just an example, you can also look at Quizno's (back in the day) and Jersey Mike's (the modern equivalent). Even my local deli serves sandwiches well beyond 800 calories as their special. It's not an interesting argument to have, though. Shops wouldn't offer these meals if folks weren't buying, and I don't believe everyone's doing take-out with the second half for dinner or lunch the next day. EDIT: Another good source to browse: https://fastfoodnutrition.org/subway https://fastfoodnutrition.org/subway You're really arguing about whether that 800 calorie run could be offset completely by a normal meal. I think it's fair to say that runners doing 800 calorie runs aren't going to Panda Express, but also at the same time: https://fastfoodnutrition.org/panda-express https://fastfoodnutrition.org/panda-express Fried rice: 520 Orange Chicken: 370 Total: 890 And most Panda Express orders include two sides, so add an extra ~300 for that (1190). I think it's fair to say that it's pretty easy for the average American to go out and buy lunch and exceed 800 calories.
lebuin 8mo ago
I think OP may be referring to the idea that the total number of calories burned in a day doesn't meaningfully change under a workout regime. Working out does burn calories, but after a few session your body starts to compensate by burning less calories in other areas (e.g. immune and reproductive system). The net result is close to zero, except in very demanding workout regimes. I don't have the background to fully evaluate how true that is. I read "Burn" by Herman Pontzer, which at least makes a very good case for it.
- jahnu 8mo ago
  So this is about https://en.wikipedia.org/wiki/Exercise_paradox https://en.wikipedia.org/wiki/Exercise_paradox I seems like it's only part of the story. If you increase exercise but also increase calorific input to match then you won't lose weight. But, the laws of energy conservation being what they are, I don't think anyone disputes that if you very significantly increase exercise but also maintain calorific input then you will lose weight as the energy must come from somewhere and there are only so many optimisations your body can make. You could of course maintain exercise levels and reduce calorific input for a similar effect, ignoring health benefits of exercise. Take an extreme case, Michael Phelps. He used to eat 12,000 cal a day because of the hours he spent swimming. Certainly not a small guy but pretty lean! So I'm totally prepared to accept there are bounds to all these statements but I still think I couldn't finish an 800 cal sandwich for lunch hehehe. By the way, I feel the Wikipedia page there uses a lot of words suggesting that the paradox isn't at all fully understood and that there could be compensating mechanisms we aren't aware of. But I'm not in a position to dig deeper.
  - danlitt 8mo ago
    > I don't think anyone disputes that if you very significantly increase exercise but also maintain calorific input then you will lose weight This is exactly what is disputed by the link you posted. They measured directly the energy expenditure (the number of calories burned by respiration) in a high-activity hunter-gatherer tribe, and in relatively low-activity industrialized societies, and found they were almost the same. So the number of calories the people consumed was not measured or relevant (and must also have been roughly the same if neither group was actively gaining weight).
wasmitnetzen 8mo ago
How can you know this "as a matter of fact"? Because your not-a-healthcare-device sportswatch tells you so?
- vbarrielle 8mo ago
  Not running, but in cycling we have power meters, and some workouts (eg 2 x 20' threshold) will definitely burn in the range of 800 calories in an hour. The energy measured by the power meter for this workout is 800 kJ for me (my threshold being around 260W). Now it turns out the conversion factor from kJ to calories is 1/4, but the body is only 25% efficient when producing calories for cycling, meaning one has to burn 4x the amount measured by the power meter. So that's 800 calories for this kind of workout, for me. I wouldn't be surprised if runners of similar fitness doing similar workouts had the same energy expenditure.
  - wasmitnetzen 8mo ago
    I'm not arguing that your body burns that much energy, that follows from the first law of thermodynamics. But whether that means that your body will have a calorie deficit of that same amount, that is much harder to prove.
sdfhbdf 8mo ago
> 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 present them with false precision that makes people treat them as ground truth. Even setting accuracy aside, the framing is the issue. Your basal metabolic rate - just keeping your organs running, blood circulating, cells maintained - accounts for 60-70% of your total daily energy expenditure. Add the thermic effect of food (~10%) and you're at roughly 70-80% of your energy budget spent before you even lace up your shoes [1]. Exercise typically makes up the remaining 20-30%. So that hour of running, while genuinely beneficial for a hundred other reasons, is a relatively small slice of your total daily burn. And not all calories are equal on the intake side either - your body spends 20-30% of the energy in protein just to digest it, compared to 0-5% for fat, so "800 kcal burned = 800 kcal of anything eaten" doesn't hold up. 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, treats all calories as interchangeable, and overweights exercise relative to what your body spends just existing. Curious though - do you track your intake with the same rigour, and if so, do you find the numbers actually add up in practice? [1]: https://my.clevelandclinic.org/health/body/basal-metabolic-rate-bmr https://my.clevelandclinic.org/health/body/basal-metabolic-r...
- jahnu 8mo ago
  Thanks for fleshing out your comment. Because initially it did kind of suggest to me you were saying it burns no calories or makes _little_ difference. I agree with all you posted. > Curious though - do you track your intake with the same rigour, and if so, do you find the numbers actually add up in practice? To return the courtesy, for the purposes of discussion I picked a rough estimate and rounded down significantly the actual amount I typically run. More often it's 1.5 hours a run and supposedly >1000 calories given my weight, heart rate, terrain, and speed. I also assumed the calculations are way overestimating my actual calories spent so just went for something somewhat plausible for the sake of a HN comment. As you noted calories aren't accurately reported by devices. I do not pay attention to it in massive detail either. But in practice since I run an average of about 25km a week but can vary from 0 for some weeks to 50 for others and I keep relatively good eye on my diet I notice significant changes in weight over time that tallies with effort. Three months of below that 20ishk a week and I will put on 2-3kg. The next three months I increase to 35ish+ a week and it drops off again. Would I swear to it in a court of law that I'm not miscounting meals? No way. But I feel reasonably comfortable that this is an accurate description.

by jahnu 8mo ago

nandomrumber 8mo ago

But you’ve never directly measured calorie expenditure while running, so how can you be certain?

nick486 8mo ago

I think it sort of depends on how you look at it. If 800 is an hour of running - that's probably "a lot" for quite a few people. But 800 is also just a sandwich. Which isn't all that much. So if you view this from a time use perspective, just skipping that sandwich is way better than running for an hour. And many people can't spare an hour a day just to make up for a sandwich. Hence - "not a lot" - Its too expensive time-wise for the caloric balance effect it provides. Just skip the sandwich instead.

BoppreH 8mo ago
I agree with the general message, but I'm curious what ingredients go in your 800 calorie sandwich. That's more than a double Big Mac with 4 patties (780 kcal)!
- mriet 8mo ago
  Lots of mayo.. and butter. It's more like a butterich, realistically. ;)
- asimovDev 8mo ago
  Maybe the Elvis sandwich https://en.wikipedia.org/wiki/Peanut_butter,_banana_and_bacon_sandwich https://en.wikipedia.org/wiki/Peanut_butter,_banana_and_baco...
jahnu 8mo ago
That's a big sandwich :) Big Mac = 580 Cal. I'm going to eat lunch one way or another and for me it's going to be under 800. Skipping meals isn't really a good choice, imo, but ok.
- tsimionescu 8mo ago
  You need to eat roughly somewhere between 1300 and 2000 Cal every day to maintain your weight even if you are doing to exercise at all. If you want to lose weight, it's far easier to remove 800 Cal from your diet, at least time wise, then it is to exercise 800 Cal's worth every day. Either way, if you're losing weight at any appreciable rate, you will feel hungry (at least if it's not chemically induced in some way, such as chemo or GLP-1 inhibitors or similar). That's just something you have to get used to if you want to lose weight.
  - jahnu 8mo ago
    > If you want to lose weight, it's far easier to remove 800 Cal from your diet, at least time wise, then it is to exercise 800 Cal's worth every day. That I absolutely agree with and so do my legs ;) I only found the suggestion that exercise _doesn't_ burn calories a bit weird. > you will feel hungry That I also agree with... all this talk of sandwiches!
    - Izkata 8mo ago
      > I only found the suggestion that exercise _doesn't_ burn calories a bit weird. I mean... No one said that? The very first comment was about how it's not a lot / not as much as people think, not that it's none.
  - sdfhbdf 8mo ago
    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 hours; 400 kcal of simple carbs will leave you hungry again in 45 minutes, in part because of the insulin and blood glucose dynamics involved. The calories in/out model isn't wrong exactly, but it's so reductionist that it becomes misleading in practice. It omits hormonal responses (insulin, leptin, ghrelin), the thermic effect differences between macronutrients (your body burns 20-30% of protein calories just processing them vs 0-5% for fat), gut microbiome composition, sleep quality, stress hormones, meal timing, and individual metabolic variation. Two people eating identical calorie counts can have very different outcomes. Telling someone "just eat less and accept the hunger" without any of that context can set them up for a miserable yo-yo cycle - or worse, a disordered relationship with food.
xnorswap 8mo ago
What kind of sandwiches are you eating? 800 calories is a ridiculously large sandwich. Even Tesco's bacon & egg triple is only 550 : https://www.tesco.com/groceries/en-GB/products/260422235 https://www.tesco.com/groceries/en-GB/products/260422235 I'm struggling to find anything I'd describe as a sandwich come close to 800 calories.
- nick486 8mo ago
  Fair enough, but so is 800cal/h exercise. And I'd rather overestimate the intake.
- rpdillon 8mo ago
  Footlong Spicy Italian at Subway ($10 sandwich) is 1320 cals. EDIT: the trend holds pretty well at the footlong size (which is a big sandwich). 18/26 sandwiches they offer are >1000 calories.
  - xnorswap 8mo ago
    A foot-long sub is not "just a sandwich", it's a meal for 2. Secondly, I can't see how you can get to 1320 calories for a footlong italian going by this: https://www.subway.com/en-gb/-/media/emea/europe/uk/nutrition/uk-and-roi-nutritional-information-june-2025.pdf https://www.subway.com/en-gb/-/media/emea/europe/uk/nutritio... Even counting footlong bread + footlong Italian Sub it only comes to ~1100. And as it makes clear, a footlong is 2 6" servings, it's disingenuous to pretend that's a sandwich.
    - rpdillon 8mo ago
      I'm talking about what happens in reality, not what the "serving size" is. Gobs of folks order a footlong at Subway and eat it for their meal. As for nitpicking on calories: the Subway site is incredibly tough to navigate. Just use https://subwaymenupedia.com/ https://subwaymenupedia.com/, since averaging across location is really tough. I wish my point were uncontroversial: millions of people buy footlongs that are over 1000 calories as a regular habit. I'm critiquing folks that are incredulous about this. Subway is just an example, you can also look at Quizno's (back in the day) and Jersey Mike's (the modern equivalent). Even my local deli serves sandwiches well beyond 800 calories as their special. It's not an interesting argument to have, though. Shops wouldn't offer these meals if folks weren't buying, and I don't believe everyone's doing take-out with the second half for dinner or lunch the next day. EDIT: Another good source to browse: https://fastfoodnutrition.org/subway https://fastfoodnutrition.org/subway You're really arguing about whether that 800 calorie run could be offset completely by a normal meal. I think it's fair to say that runners doing 800 calorie runs aren't going to Panda Express, but also at the same time: https://fastfoodnutrition.org/panda-express https://fastfoodnutrition.org/panda-express Fried rice: 520 Orange Chicken: 370 Total: 890 And most Panda Express orders include two sides, so add an extra ~300 for that (1190). I think it's fair to say that it's pretty easy for the average American to go out and buy lunch and exceed 800 calories.

lebuin 8mo ago

I think OP may be referring to the idea that the total number of calories burned in a day doesn't meaningfully change under a workout regime. Working out does burn calories, but after a few session your body starts to compensate by burning less calories in other areas (e.g. immune and reproductive system). The net result is close to zero, except in very demanding workout regimes. I don't have the background to fully evaluate how true that is. I read "Burn" by Herman Pontzer, which at least makes a very good case for it.

jahnu 8mo ago
So this is about https://en.wikipedia.org/wiki/Exercise_paradox https://en.wikipedia.org/wiki/Exercise_paradox I seems like it's only part of the story. If you increase exercise but also increase calorific input to match then you won't lose weight. But, the laws of energy conservation being what they are, I don't think anyone disputes that if you very significantly increase exercise but also maintain calorific input then you will lose weight as the energy must come from somewhere and there are only so many optimisations your body can make. You could of course maintain exercise levels and reduce calorific input for a similar effect, ignoring health benefits of exercise. Take an extreme case, Michael Phelps. He used to eat 12,000 cal a day because of the hours he spent swimming. Certainly not a small guy but pretty lean! So I'm totally prepared to accept there are bounds to all these statements but I still think I couldn't finish an 800 cal sandwich for lunch hehehe. By the way, I feel the Wikipedia page there uses a lot of words suggesting that the paradox isn't at all fully understood and that there could be compensating mechanisms we aren't aware of. But I'm not in a position to dig deeper.
- danlitt 8mo ago
  > I don't think anyone disputes that if you very significantly increase exercise but also maintain calorific input then you will lose weight This is exactly what is disputed by the link you posted. They measured directly the energy expenditure (the number of calories burned by respiration) in a high-activity hunter-gatherer tribe, and in relatively low-activity industrialized societies, and found they were almost the same. So the number of calories the people consumed was not measured or relevant (and must also have been roughly the same if neither group was actively gaining weight).

wasmitnetzen 8mo ago

How can you know this "as a matter of fact"? Because your not-a-healthcare-device sportswatch tells you so?

vbarrielle 8mo ago
Not running, but in cycling we have power meters, and some workouts (eg 2 x 20' threshold) will definitely burn in the range of 800 calories in an hour. The energy measured by the power meter for this workout is 800 kJ for me (my threshold being around 260W). Now it turns out the conversion factor from kJ to calories is 1/4, but the body is only 25% efficient when producing calories for cycling, meaning one has to burn 4x the amount measured by the power meter. So that's 800 calories for this kind of workout, for me. I wouldn't be surprised if runners of similar fitness doing similar workouts had the same energy expenditure.
- wasmitnetzen 8mo ago
  I'm not arguing that your body burns that much energy, that follows from the first law of thermodynamics. But whether that means that your body will have a calorie deficit of that same amount, that is much harder to prove.

sdfhbdf 8mo ago

> 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 present them with false precision that makes people treat them as ground truth. Even setting accuracy aside, the framing is the issue. Your basal metabolic rate - just keeping your organs running, blood circulating, cells maintained - accounts for 60-70% of your total daily energy expenditure. Add the thermic effect of food (~10%) and you're at roughly 70-80% of your energy budget spent before you even lace up your shoes [1]. Exercise typically makes up the remaining 20-30%. So that hour of running, while genuinely beneficial for a hundred other reasons, is a relatively small slice of your total daily burn. And not all calories are equal on the intake side either - your body spends 20-30% of the energy in protein just to digest it, compared to 0-5% for fat, so "800 kcal burned = 800 kcal of anything eaten" doesn't hold up. 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, treats all calories as interchangeable, and overweights exercise relative to what your body spends just existing. Curious though - do you track your intake with the same rigour, and if so, do you find the numbers actually add up in practice? [1]: https://my.clevelandclinic.org/health/body/basal-metabolic-rate-bmr https://my.clevelandclinic.org/health/body/basal-metabolic-r...

jahnu 8mo ago
Thanks for fleshing out your comment. Because initially it did kind of suggest to me you were saying it burns no calories or makes _little_ difference. I agree with all you posted. > Curious though - do you track your intake with the same rigour, and if so, do you find the numbers actually add up in practice? To return the courtesy, for the purposes of discussion I picked a rough estimate and rounded down significantly the actual amount I typically run. More often it's 1.5 hours a run and supposedly >1000 calories given my weight, heart rate, terrain, and speed. I also assumed the calculations are way overestimating my actual calories spent so just went for something somewhat plausible for the sake of a HN comment. As you noted calories aren't accurately reported by devices. I do not pay attention to it in massive detail either. But in practice since I run an average of about 25km a week but can vary from 0 for some weeks to 50 for others and I keep relatively good eye on my diet I notice significant changes in weight over time that tallies with effort. Three months of below that 20ishk a week and I will put on 2-3kg. The next three months I increase to 35ish+ a week and it drops off again. Would I swear to it in a court of law that I'm not miscounting meals? No way. But I feel reasonably comfortable that this is an accurate description.