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Tangentially related question: one cause of cancer would be lack of physical activity (https://www.who.int/news-room/fact-sheets/detail/cancer https://www.who.i

Tangentially related question: one cause of cancer would be lack of physical activity (https://www.who.int/news-room/fact-sheets/detail/cancer https://www.who.int/news-room/fact-sheets/detail/cancer). What's the mechanism of this? Cancer is caused by bad-luck random cell division creating a bad cell, I can see how chemicals influence this process, but how does physical activity?

blueflow 2y ago
Higher fitness -> higher chance the immune system will kill the rogue cells on its own.
- bdjsiqoocwk 2y ago
  What's the mechanism behind that? Being "more fit" is not exactly one single thing.
- xdavidliu 2y ago
  is it obvious that good fitness is related to good immune function?
  - blueflow 2y ago
    It seems obvious when you see your own body aging and slowly loose both.
- TeMPOraL 2y ago
  I'd expect the opposite: higher fitness -> immune system more busy with repairing wear&tear. Lower fitness -> immune system bored and more reactive to any suspicious cellular activity.
  - inciampati 2y ago
    The repair of the wear and tear seems to provide more opportunities for the body to reject cancers. Also, aerobic activity may encourage selection for oxidative metabolism which is very suppressed in most cancers. It's counterintuitive but the epidemiology is very clear that exercise is protective. It doesn't wear you out faster but rather helps you rebuild and maintain yourself more rapidly (without which, you wear out).
  - dahart 2y ago
    That might be true in the extreme ends, say for Ironman athletes, but a bit misleading as a summary since we already have lots of data that moderate exercise correllates with reduced risks of everything from getting a cold to heart disease. If we’re comparing to people who don’t exercise, the alternative should be moderate exercise, not high intensity training. Also a bored and over-reactive immune system can be a pretty bad thing.
  - rdedev 2y ago
    When it comes to dealing with any biological systems always look for outcomes over mechanisms. There is plenty of evidence showing exercise improves almost all markets of health
Iulioh 2y ago
I never found a reason BUT my personal opinion is: Probably putting some "stress" on the cells is beneficial, is like forcing them to work a little once in a while instead of letting them function in the "just survive" mode. Maybe blood circulation? It may clean toxins from where the blood may flow slower? That's my headcanon
- AtlasBarfed 2y ago
  Whatever science I read on this seems to indicate that the exercise induces a high amount of oxidative molecule release in your cells. That should be bad for the body because that results in oxidative damage. But of course we've evolved mechanisms to compensate. For that, there's a corresponding release of antioxidants and cellular repair to deal with the oxidation events of exercise. Exercise in general raises your immune system as well. Your immune system cleans up a lot of rogue mutation cells. It may also be the physical activity increases massive amounts of blood flow through your entire system and helps at a macro level with this cleanup of deviant cells. But I'm not an oncologist nor am I a physiological biologist.
- paulsmith 2y ago
  Hearing the evolutionary anthropologist Herman Pontzer talk about this was really eye-opening for me: https://www.msnbc.com/msnbc-podcast/examining-energy-evolution-herman-pontzer-podcast-transcript-n1270125 https://www.msnbc.com/msnbc-podcast/examining-energy-evoluti... "[Y]ou can think about all these processes as competing for calories over the course of the day. And normally, low priority things like having a really high inflammation response or having a high stress response, those get tamped down in a highly active population like we've all evolved in. But now, you move to these weird zoos that we've built ourselves, where you don't have to be active, food's available all over the place, energy supply is really easy. And now, these low priority activities which used to probably only happen very occasionally in the past, in the deep past, now are happening all the time, chronically, at these super high levels, and it's actually really bad for you."
  - card_zero 2y ago
    That's a good read. But one of the processes competing for calories is the immune system. > If you take somebody who is really sedentary and you get them exercising, what happens? Things like inflammation, which is your immune system being overactive, goes down. [Also cortisol level when under stress, and reproductive hormone levels, go down.] So that puts a small hole in the "exercise helps the immune system clear up cancer" theory. Maybe it in fact stops the immune system causing cancer. Or maybe it does both things, since biology is messy and the immune system might have multiple energy budgets for all I know.
krisoft 2y ago
> What's the mechanism of this? It doesn’t necessarily have an easy to understand soundbite explanation. Biology is like spagetti code. Everything depends on everything in difficult to comprehend ways.
inglor_cz 2y ago
Cancer is caused by bad-luck random cell division creating a bad cell That is only the first necessary step towards cancer. Our bodies have various mechanisms to kill suspicious cells before they start being a systemic problem. Apoptosis, or the immune system attacking them if they can be recognized. These mechanisms are pretty efficient; in the animal world, animals with really strong immune systems, like bats, very rarely get cancer. And most of our current progress against cancer involves ... very careful stimulation of the immune system against targets specific for that particular patient's tumor. Physical activity can probably influence these anti-cancer mechanisms, as does aging etc.
photochemsyn 2y ago
The simplest explanation is that physical activity increases blood circulation and lung ventilation, which (as long as one is not exercising in a polluted environment) helps the liver and kidneys process and excrete various toxins at a greater rate. It also reduces body fat, which can store fat-soluble toxins. There's also a high likelihood that people who get regular exercise are also eating healthier food that hasn't been highly processed and loaded up with pesticide residue, biocides that slow fungal and bacterial growth, animal growth hormones, etc. The fundamental equation is something like: (body load of toxins) = (ingestion rate) - (excretion rate)
whimsicalism 2y ago
well there’s the obvious pathway that people who exercise regularly tend to have fewer number of cells than those who don’t e: okay, not the pathway - but we do know that additional weight increases cancer risk
- anon84873628 2y ago
  Except that adipose cells don't undergo mitosis. When is the last time you heard someone dying of "fat cancer"? Believe it or not, professional researchers probably tried to think of "obvious pathways" too.
  - whimsicalism 2y ago
    i wasn’t claiming professional researchers didn’t know something, so not sure where you are pulling that from. i guess the mechanism correlating weight and cancer is more complex than “more cells more cancer”, but the correlation is still well measured and i assume a reason why physical exercise would anti-correlate as well e: also my understanding was non-adipose cell count was also correlated as weight
    - anon84873628 2y ago
      Of course there is a correlation. You were proposing an "obvious" explanation for it based on relative cell counts, which "obviously" is not correct if you consider the nature of the tissues involved.
      - whimsicalism 2y ago
        Oh definitely. It wasn’t clear from my above comment, but I acknowledge that bit was definitely wrong and will eat crow for that. I guess the main thing I was trying to say was that we know obesity is correlated with cancer and I thought we had some understanding of the mechanism behind that, so my guess is that physical exercise is just the inverse of that mechanism?
  - copperx 2y ago
Jtsummers 2y ago
A significant risk factor for some cancers is chronic inflammation. Physical activity can help with that directly, but also indirectly as it can help reduce weight (diet is more important there). Reducing/eliminating chronic inflammation is generally a good thing anyways for other health concerns besides just cancer.
CuriouslyC 2y ago
Exercise induces stress which triggers a systemic hormetic response. That response makes cells more resistant to random errors. Additionally, that stress can trigger apoptosis in senescent or unhealthy cells.
dahart 2y ago
Here’s a meta-study on the mechanisms for the benefits of moderate exercise, and it includes a sizeable list of different chemical changes in the body that exercise promotes: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9923435/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9923435/
rKarpinski 2y ago
A cutting edge theory is that exercise can interfere's with cancer's metabolism (Warburg Effect) and helps to regulate lactate levels which chronically dis-regulated will promote cancer. "Specifically, we posit that in carcinogenesis aberrant cell signaling due to exaggerated and continually high lactate levels yields an (inappropriate) positive feedback loop" [1] https://academic.oup.com/carcin/article/38/2/119/2709442 https://academic.oup.com/carcin/article/38/2/119/2709442
techjamie 2y ago
Recent science suggests that the body adjusts to burn approximately the same amount of calories per day, given a consistent amount of activity, regardless of how much activity there actually is. So, a person with an active lifestyle will burn approximately the average 2,000 calories, but a person at rest will also burn about the same number. I'm oversimplifying massively, but essentially, the theory is that if you don't give your body an outlet to burn with, it will burn the calories on things that aren't good for you. Eg, increasing inflammation. It wouldn't surprise me if some of these effects are contributing factors. Source: https://youtu.be/vSSkDos2hzo?si=CrPh2_vLRqHG0Z3i https://youtu.be/vSSkDos2hzo?si=CrPh2_vLRqHG0Z3i

blueflow 2y ago

Higher fitness -> higher chance the immune system will kill the rogue cells on its own.

bdjsiqoocwk 2y ago
What's the mechanism behind that? Being "more fit" is not exactly one single thing.
xdavidliu 2y ago
is it obvious that good fitness is related to good immune function?
- blueflow 2y ago
  It seems obvious when you see your own body aging and slowly loose both.
TeMPOraL 2y ago
I'd expect the opposite: higher fitness -> immune system more busy with repairing wear&tear. Lower fitness -> immune system bored and more reactive to any suspicious cellular activity.
- inciampati 2y ago
  The repair of the wear and tear seems to provide more opportunities for the body to reject cancers. Also, aerobic activity may encourage selection for oxidative metabolism which is very suppressed in most cancers. It's counterintuitive but the epidemiology is very clear that exercise is protective. It doesn't wear you out faster but rather helps you rebuild and maintain yourself more rapidly (without which, you wear out).
- dahart 2y ago
  That might be true in the extreme ends, say for Ironman athletes, but a bit misleading as a summary since we already have lots of data that moderate exercise correllates with reduced risks of everything from getting a cold to heart disease. If we’re comparing to people who don’t exercise, the alternative should be moderate exercise, not high intensity training. Also a bored and over-reactive immune system can be a pretty bad thing.
- rdedev 2y ago
  When it comes to dealing with any biological systems always look for outcomes over mechanisms. There is plenty of evidence showing exercise improves almost all markets of health

Iulioh 2y ago

I never found a reason BUT my personal opinion is: Probably putting some "stress" on the cells is beneficial, is like forcing them to work a little once in a while instead of letting them function in the "just survive" mode. Maybe blood circulation? It may clean toxins from where the blood may flow slower? That's my headcanon

AtlasBarfed 2y ago
Whatever science I read on this seems to indicate that the exercise induces a high amount of oxidative molecule release in your cells. That should be bad for the body because that results in oxidative damage. But of course we've evolved mechanisms to compensate. For that, there's a corresponding release of antioxidants and cellular repair to deal with the oxidation events of exercise. Exercise in general raises your immune system as well. Your immune system cleans up a lot of rogue mutation cells. It may also be the physical activity increases massive amounts of blood flow through your entire system and helps at a macro level with this cleanup of deviant cells. But I'm not an oncologist nor am I a physiological biologist.
paulsmith 2y ago
Hearing the evolutionary anthropologist Herman Pontzer talk about this was really eye-opening for me: https://www.msnbc.com/msnbc-podcast/examining-energy-evolution-herman-pontzer-podcast-transcript-n1270125 https://www.msnbc.com/msnbc-podcast/examining-energy-evoluti... "[Y]ou can think about all these processes as competing for calories over the course of the day. And normally, low priority things like having a really high inflammation response or having a high stress response, those get tamped down in a highly active population like we've all evolved in. But now, you move to these weird zoos that we've built ourselves, where you don't have to be active, food's available all over the place, energy supply is really easy. And now, these low priority activities which used to probably only happen very occasionally in the past, in the deep past, now are happening all the time, chronically, at these super high levels, and it's actually really bad for you."
- card_zero 2y ago
  That's a good read. But one of the processes competing for calories is the immune system. > If you take somebody who is really sedentary and you get them exercising, what happens? Things like inflammation, which is your immune system being overactive, goes down. [Also cortisol level when under stress, and reproductive hormone levels, go down.] So that puts a small hole in the "exercise helps the immune system clear up cancer" theory. Maybe it in fact stops the immune system causing cancer. Or maybe it does both things, since biology is messy and the immune system might have multiple energy budgets for all I know.

krisoft 2y ago

> What's the mechanism of this? It doesn’t necessarily have an easy to understand soundbite explanation. Biology is like spagetti code. Everything depends on everything in difficult to comprehend ways.

inglor_cz 2y ago

Cancer is caused by bad-luck random cell division creating a bad cell That is only the first necessary step towards cancer. Our bodies have various mechanisms to kill suspicious cells before they start being a systemic problem. Apoptosis, or the immune system attacking them if they can be recognized. These mechanisms are pretty efficient; in the animal world, animals with really strong immune systems, like bats, very rarely get cancer. And most of our current progress against cancer involves ... very careful stimulation of the immune system against targets specific for that particular patient's tumor. Physical activity can probably influence these anti-cancer mechanisms, as does aging etc.

photochemsyn 2y ago

The simplest explanation is that physical activity increases blood circulation and lung ventilation, which (as long as one is not exercising in a polluted environment) helps the liver and kidneys process and excrete various toxins at a greater rate. It also reduces body fat, which can store fat-soluble toxins. There's also a high likelihood that people who get regular exercise are also eating healthier food that hasn't been highly processed and loaded up with pesticide residue, biocides that slow fungal and bacterial growth, animal growth hormones, etc. The fundamental equation is something like: (body load of toxins) = (ingestion rate) - (excretion rate)

whimsicalism 2y ago

well there’s the obvious pathway that people who exercise regularly tend to have fewer number of cells than those who don’t e: okay, not the pathway - but we do know that additional weight increases cancer risk

anon84873628 2y ago
Except that adipose cells don't undergo mitosis. When is the last time you heard someone dying of "fat cancer"? Believe it or not, professional researchers probably tried to think of "obvious pathways" too.
- whimsicalism 2y ago
  i wasn’t claiming professional researchers didn’t know something, so not sure where you are pulling that from. i guess the mechanism correlating weight and cancer is more complex than “more cells more cancer”, but the correlation is still well measured and i assume a reason why physical exercise would anti-correlate as well e: also my understanding was non-adipose cell count was also correlated as weight
  - anon84873628 2y ago
    Of course there is a correlation. You were proposing an "obvious" explanation for it based on relative cell counts, which "obviously" is not correct if you consider the nature of the tissues involved.
    - whimsicalism 2y ago
      Oh definitely. It wasn’t clear from my above comment, but I acknowledge that bit was definitely wrong and will eat crow for that. I guess the main thing I was trying to say was that we know obesity is correlated with cancer and I thought we had some understanding of the mechanism behind that, so my guess is that physical exercise is just the inverse of that mechanism?
- copperx 2y ago

Jtsummers 2y ago

A significant risk factor for some cancers is chronic inflammation. Physical activity can help with that directly, but also indirectly as it can help reduce weight (diet is more important there). Reducing/eliminating chronic inflammation is generally a good thing anyways for other health concerns besides just cancer.

CuriouslyC 2y ago

Exercise induces stress which triggers a systemic hormetic response. That response makes cells more resistant to random errors. Additionally, that stress can trigger apoptosis in senescent or unhealthy cells.

dahart 2y ago

Here’s a meta-study on the mechanisms for the benefits of moderate exercise, and it includes a sizeable list of different chemical changes in the body that exercise promotes: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9923435/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9923435/

rKarpinski 2y ago

A cutting edge theory is that exercise can interfere's with cancer's metabolism (Warburg Effect) and helps to regulate lactate levels which chronically dis-regulated will promote cancer. "Specifically, we posit that in carcinogenesis aberrant cell signaling due to exaggerated and continually high lactate levels yields an (inappropriate) positive feedback loop" [1] https://academic.oup.com/carcin/article/38/2/119/2709442 https://academic.oup.com/carcin/article/38/2/119/2709442

techjamie 2y ago

Recent science suggests that the body adjusts to burn approximately the same amount of calories per day, given a consistent amount of activity, regardless of how much activity there actually is. So, a person with an active lifestyle will burn approximately the average 2,000 calories, but a person at rest will also burn about the same number. I'm oversimplifying massively, but essentially, the theory is that if you don't give your body an outlet to burn with, it will burn the calories on things that aren't good for you. Eg, increasing inflammation. It wouldn't surprise me if some of these effects are contributing factors. Source: https://youtu.be/vSSkDos2hzo?si=CrPh2_vLRqHG0Z3i https://youtu.be/vSSkDos2hzo?si=CrPh2_vLRqHG0Z3i