9 ms·

One Twin Exercises, the Other Doesn’t

145 points by igonvalue 12y ago

probono1 12y ago
The full data set seems to show that the strongest argument in the article is that propensity to fitness is mostly a result of genetics and upbringing - it was apparently very difficult to find twins where the level of fitness was different, and very difficult to find twins with significantly different dietary preferences. This seems to indicate that in most cases, your level of fitness is basically pre-determined by age 18.
- yaddayadda 12y ago
  The authors did acknowledge the difficulty of finding twins with different fitness levels: >The researchers were looking for young adult identical twins in their early- to mid-20s whose exercise habits had substantially diverged after they had left their childhood homes. These twins were not easy to find. Most of the pairs had maintained remarkably similar exercise routines, despite living apart. And they also highlight that while the genetics and environment play a huge part they don't preclude change: >More subtly, the findings also point out that genetics and environment “do not have to be” destiny when it comes to exercise habits, Dr. Kujala said. For these particular twins, whether their genes and childhoods nudged them toward exercising regularly or slumping on the couch, one of the pair overcame that legacy and did the opposite (for better and worse).
- tghw 12y ago
  Propensity and pre-determination are very different things. The whole point of the article is that someone who makes fitness a priority and exercises regularly has better health and fitness indicators than someone who doesn't, all else being equal. Being active is a choice (for most people). Certainly, some people are more likely to do it naturally, but that doesn't preclude the rest of us from doing it.
  - DougWebb 12y ago
    It might also show that someone who has better health and fitness indicators is more likely to exercise regularly. Maybe environmental concerns (eg: stress) impact your health and fitness indicators, which causes a lack of motivation and energy for exercise that you would normally have without the stress. I know, as an overweight and highly stressed person, that I often feel that way about exercise.
- vlasev 12y ago
  No no. They are talking about habits here. Twins are more likely to have the same kinds of diets and exercises and overall similar lives, which in turn lead to them being in similar shape. It was difficult for them to find divergent twins. But once you are looking at divergent twins they the exercise and lifestyle became quite important. Your habits and lifestyle are basically pre-determined by a certain age but as the article shows, they are not set in stone because lifestyles may change.
waynecochran 12y ago
Amazing. The twin that exercized looked different and was more healthy.
- jostmey 12y ago
  Is that an actual picture of the twins?
  - kafene 12y ago
    My guess is that that's a picture from the art department.
    - alecdbrooks 12y ago
      It's attributed to Getty Images, so it's actually a stock photo.
- oliv__ 12y ago
  lol
Udik 12y ago
I wonder if they took in account the fact that, as they say, the twin that stopped exercising did so reluctantly and in response to some social or family pressure. In other words, they're comparing a person who keeps doing what he always liked to do with another that had to give up. I'm not sure the result can be transferred to people who never felt the urge and benefit of exercising. How would compare two twins, one of which has only in recent years being forced to exercise?
- revelation 12y ago
  Whats your point here, motivation is necessary to realize benefits from training? And the absence causes body fat to accumulate?
  - bsder 12y ago
    Actually, yes. There have been several studies that seem to point towards significantly less benefit from exercise when people don't enjoy it. Obviously, this is really hard to control for since those who enjoy exercise less are less likely to do it, push themselves, etc. That's not to say that exercise doesn't help at all, but since many of us are concerned about efficiency of exercise that's an important finding.
    - sliverstorm 12y ago
      Another key one would be, less likely to do it well... The more I learn about exercise & fitness, the more I discover it is a learned skill. For a simple example, despite the fact that my push-ups looked ok, I was in fact doing them terribly wrong all my life which meant they did absolutely nothing to strengthen my pectorals. You might think something as simple as a push-up would be hard to do wrong...
    - lurknomore 12y ago
      Intensity matters. Improvement is gained via progressive overload. Showing up but half-assing it is a great way to not make progress and inevitably come to resent the activity (minimal benefits for the time & work involved), thus perpetuating a vicious cycle.
Timothee 12y ago
I'll admit I didn't read the study but the results summarized in this post don't seem very interesting: The sedentary twins had lower endurance capacities, higher body fat percentages, and signs of insulin resistance, signaling the onset of metabolic problems. The active twins had significantly more grey matter than the sedentary twins, especially in areas of the brain involved in motor control and coordination. Isn't this expected to anybody not exercising vs. someone who is? It would have been interesting to see if there were results beyond the obvious effects of exercising.
- hayksaakian 12y ago
  what's interesting is that this comparison controls for genetics, given that they're twins.
  - Timothee 12y ago
    I get that, but I feel like we've known for quite a while that people who exercise can run longer and have lower body fat, regardless of genetics. Genetics can affect how long you can run compared to others, but you will run longer if you exercise than if you don't. If you take anybody in the world and have them exercise, they'll lower their body fat, everything else being equal, no? And that's not only the same genes, it's actually the same person.
    - jschwartzi 12y ago
      I thought, too, that genetics only controls for something akin to a few percent of your potential, and that to bump up against that limit you would have to already be in the 99th percentile for a particular capability. So your endurance is controlled by past training almost exclusively.
  - simonster 12y ago
    You can control for genetics by running a controlled study, where you take a group of people and randomly assign some individuals to exercise and some individuals not to. Then, by construction, the exercise and no exercise groups are drawn from the same genetic distribution. I'd be very surprised if no one has tried to do this, but there's probably a limit on how long you could run it for. There's also the possible "placebo effect" confound, which is a problem for both a controlled study and a twin study, but might be a bigger issue for the former (where participants are told to exercise) than the latter (where participants exercise or don't exercise of their own volition).
AstroChimpHam 12y ago
>But eventually the researchers homed in on 10 pairs of male identical twins, one of whom regularly exercised, while the other did not, usually because of work or family pressures, the researchers determined. That "work and family pressure" sounds like stress and a pretty important confounding variable.
- reedlaw 12y ago
  It's also a choice, or even an excuse. Nearly everyone has work and family pressures. Some find relief in exercise.
  - maratd 12y ago
    > It's also a choice, or even an excuse. Alright, get off your high horse. Just because you "excercise" doesn't make you better. There are plenty who don't need to because they work with their hands and plenty more because they have active hobbies. And while it's a popular notion that constant activity makes you healthier, it's just common sense that the body is a machine and the more you stress a machine, the likelier it is to break. See athletes for common ailments.
    - samcal 12y ago
      > There are plenty who don't need to because they work with their hands and plenty more because they have active hobbies. And I bet those aren't the people about whom the parent was talking. It's not as if the benefits of exercise are unknown or controversial. Everyone knows that they are better off being active. Therefore, people who do not spend time being active are at the very least making a choice, if they legitimately have a more effective way of benefitting themselves, at most making excuses, if they do not have such a way.
    - omegaham 12y ago
      > See athletes for common ailments. This is a good point, and it's a good idea to pick a form of exercise that has less impact, (at an extreme end, I'm sure that the skiiers who do mogul racing are in great shape, but their knees probably don't work so well after a few years) but keep in mind that the body repairs itself. As long as you aren't repeatedly destroying your joints, you're going to get a lot of benefits from exercise. In many cases, athletes are less likely to get injured than the sedentary population because of increased strength and flexibility.
deleted 12y ago
[deleted]
gwern 12y ago
Fulltext: https://www.dropbox.com/s/gfch760k1ratwo3/2015-rottensteiner.pdf https://www.dropbox.com/s/gfch760k1ratwo3/2015-rottensteiner... / http://sci-hub.org/downloads/045f/10.0000@pdfs.journals.lww.com@generic-FD16BBD9129B.pdf http://sci-hub.org/downloads/045f/10.0000@pdfs.journals.lww.... Buried some interesting points there: > The researchers were looking for young adult identical twins in their early- to mid-20s whose exercise habits had substantially diverged after they had left their childhood homes. These twins were not easy to find. Most of the pairs had maintained remarkably similar exercise routines, despite living apart. Besides the testament to how 'everything is heritable' inherent in that observation, it also raises the question: if they are so unusual, doesn't that make confounding more plausible? > Interestingly, the twins tended to have very similar diets, whatever their workout routines, so food choices were unlikely to have contributed to health differences. Also very interesting, and counter to the usual narratives about health. (Everything is heritable...) > The twins’ brains also were unalike. The active twins had significantly more grey matter than the sedentary twins, especially in areas of the brain involved in motor control and coordination. Warning sign: 'significantly'. Does this mean, as any ordinary person would take it to mean (in conjunction with that lazy stock photo), 'a lot' or does it mean 'p<0.05'? Trick question, of course it means the latter, which is useless! Take a look at the fulltext, pg6, table 2, which spits out the actual differences between the twin pairs. I hope you're ready to be wowed by how much difference an exercise regimen makes when you control for genetics (picking out a few I recognize): 1. BMI: -0.8 2. VO2max: 6.3 3. weight: -2kg 4. waist circumference: -3.3cm 5. fat percentage: -3.3 (!) 6. lean mass: 1.4kg I'm not sure I've seen such a damning indictment of exercise in a long time. (Less than 1 on BMI? 2kg of weight? I fluctuate more than that on a weekly basis...)
- lurknomore 12y ago
  There are several sayings in fitness circles that are similar to this: "You can't outrun your fork." Diet is the primary reason people are obese, not lack of exercise.
  - peteretep 12y ago
    I was about to post "can't outrun a fork" too. Hour of running five days a week burns only enough calories two account for two super-sized Big Mac meals.
bootload 12y ago
we can “move more,” surprisingly this is difficult, not impossible. Back in 2007 I did a simple experiment myself asking, 'at what point do you fail when repeating exercising?' The idea was pretty simple: pick a arbitrary impossible distance to cover and move each day to reach it. The impossible distance I chose 1000km in a year. So I selected a difficult 10km source and set out each day moving 10km per day until I complete my target. I reached my target by late November and decided to push-on to 1000Ml (1600Km), the last 400 in 20 days. The key failure point I found? Just before I started. If you could psychologically push through any excuse made not to go, just before you started, It's pretty likely you will start and finish. I keep this up averaging about 2000km/yr using that insight into failure. Up to 300km so far this year (with min/max 1kg weight and 8kg pack).
deleted 12y ago
[deleted]
mathattack 12y ago
"But eventually the researchers homed in on 10 pairs of male identical twins, one of whom regularly exercised, while the other did not, usually because of work or family pressures, the researchers determined." Oh boy... How can 10 possibly be enough?
laichzeit0 12y ago
I always find it interesting that whenever exercise/diet topics come up on HN that people will go to the n-th degree to try and discredit or rubbish the studies. Could it be a bias in the stereotypical geek which shuns both these habits and so seeks an intellectual reason to justify his sedentary lifestyle?
- philjackson 12y ago
  It's a cynical view, but I'm afraid to say I feel it too. This whole 'body acceptance' movement (in the context of obesity) that's happening at the moment is detrimental to society and should probably be shunned as overweight people justifying their inactive lifestyles.
parag_c_mehta 12y ago
Would have been great if some pictures were shared. Mere numbers do not tell full story that gets shown in actual pictures.
gadders 12y ago
From the report: "The scientists invited these twins into the lab and measured each young man’s endurance capacity, body composition and insulin sensitivity, to determine their fitness and metabolic health." Shame they couldn't find twins that took part in strength training, but not surprising given the difficulties in finding any participants.
Kiro 12y ago
> The active twins had significantly more grey matter than the sedentary twins, especially in areas of the brain involved in motor control and coordination. Is that good or bad?
- pingou 12y ago
  That looks good to me. What I'm wondering if that it only means that people have better motor control or coordination, or that it can also help people be good at math, for example, or at least help them if they decide to learn math?
darkhorn 12y ago
Can someone explain to me why an identical twin is allergic to mushrooms and the other one is not? Also why a symmetric identical twin is more friendly/outgoing and speaks fluently while the other one is opposite?
- kristiandupont 12y ago
  Without knowing any specific details, I can still answer that: because both allergies and personality are not (completely) dependent on nature, but to some extent on nurture.
- jepper 12y ago
  Because your immune system, a highly complex interaction between countless cells, is not fully determined just by your genes or your environment. There is also a stochastic factor.

145 points by igonvalue 12y ago

The full data set seems to show that the strongest argument in the article is that propensity to fitness is mostly a result of genetics and upbringing - it was apparently very difficult to find twins where the level of fitness was different, and very difficult to find twins with significantly different dietary preferences. This seems to indicate that in most cases, your level of fitness is basically pre-determined by age 18.

yaddayadda 12y ago
The authors did acknowledge the difficulty of finding twins with different fitness levels: >The researchers were looking for young adult identical twins in their early- to mid-20s whose exercise habits had substantially diverged after they had left their childhood homes. These twins were not easy to find. Most of the pairs had maintained remarkably similar exercise routines, despite living apart. And they also highlight that while the genetics and environment play a huge part they don't preclude change: >More subtly, the findings also point out that genetics and environment “do not have to be” destiny when it comes to exercise habits, Dr. Kujala said. For these particular twins, whether their genes and childhoods nudged them toward exercising regularly or slumping on the couch, one of the pair overcame that legacy and did the opposite (for better and worse).
tghw 12y ago
Propensity and pre-determination are very different things. The whole point of the article is that someone who makes fitness a priority and exercises regularly has better health and fitness indicators than someone who doesn't, all else being equal. Being active is a choice (for most people). Certainly, some people are more likely to do it naturally, but that doesn't preclude the rest of us from doing it.
- DougWebb 12y ago
  It might also show that someone who has better health and fitness indicators is more likely to exercise regularly. Maybe environmental concerns (eg: stress) impact your health and fitness indicators, which causes a lack of motivation and energy for exercise that you would normally have without the stress. I know, as an overweight and highly stressed person, that I often feel that way about exercise.
vlasev 12y ago
No no. They are talking about habits here. Twins are more likely to have the same kinds of diets and exercises and overall similar lives, which in turn lead to them being in similar shape. It was difficult for them to find divergent twins. But once you are looking at divergent twins they the exercise and lifestyle became quite important. Your habits and lifestyle are basically pre-determined by a certain age but as the article shows, they are not set in stone because lifestyles may change.

waynecochran 12y ago

Amazing. The twin that exercized looked different and was more healthy.

jostmey 12y ago
Is that an actual picture of the twins?
- kafene 12y ago
  My guess is that that's a picture from the art department.
  - alecdbrooks 12y ago
    It's attributed to Getty Images, so it's actually a stock photo.
oliv__ 12y ago
lol

Udik 12y ago

I wonder if they took in account the fact that, as they say, the twin that stopped exercising did so reluctantly and in response to some social or family pressure. In other words, they're comparing a person who keeps doing what he always liked to do with another that had to give up. I'm not sure the result can be transferred to people who never felt the urge and benefit of exercising. How would compare two twins, one of which has only in recent years being forced to exercise?

revelation 12y ago
Whats your point here, motivation is necessary to realize benefits from training? And the absence causes body fat to accumulate?
- bsder 12y ago
  Actually, yes. There have been several studies that seem to point towards significantly less benefit from exercise when people don't enjoy it. Obviously, this is really hard to control for since those who enjoy exercise less are less likely to do it, push themselves, etc. That's not to say that exercise doesn't help at all, but since many of us are concerned about efficiency of exercise that's an important finding.
  - sliverstorm 12y ago
    Another key one would be, less likely to do it well... The more I learn about exercise & fitness, the more I discover it is a learned skill. For a simple example, despite the fact that my push-ups looked ok, I was in fact doing them terribly wrong all my life which meant they did absolutely nothing to strengthen my pectorals. You might think something as simple as a push-up would be hard to do wrong...
  - lurknomore 12y ago
    Intensity matters. Improvement is gained via progressive overload. Showing up but half-assing it is a great way to not make progress and inevitably come to resent the activity (minimal benefits for the time & work involved), thus perpetuating a vicious cycle.

Timothee 12y ago

I'll admit I didn't read the study but the results summarized in this post don't seem very interesting: The sedentary twins had lower endurance capacities, higher body fat percentages, and signs of insulin resistance, signaling the onset of metabolic problems. The active twins had significantly more grey matter than the sedentary twins, especially in areas of the brain involved in motor control and coordination. Isn't this expected to anybody not exercising vs. someone who is? It would have been interesting to see if there were results beyond the obvious effects of exercising.

hayksaakian 12y ago
what's interesting is that this comparison controls for genetics, given that they're twins.
- Timothee 12y ago
  I get that, but I feel like we've known for quite a while that people who exercise can run longer and have lower body fat, regardless of genetics. Genetics can affect how long you can run compared to others, but you will run longer if you exercise than if you don't. If you take anybody in the world and have them exercise, they'll lower their body fat, everything else being equal, no? And that's not only the same genes, it's actually the same person.
  - jschwartzi 12y ago
    I thought, too, that genetics only controls for something akin to a few percent of your potential, and that to bump up against that limit you would have to already be in the 99th percentile for a particular capability. So your endurance is controlled by past training almost exclusively.
- simonster 12y ago
  You can control for genetics by running a controlled study, where you take a group of people and randomly assign some individuals to exercise and some individuals not to. Then, by construction, the exercise and no exercise groups are drawn from the same genetic distribution. I'd be very surprised if no one has tried to do this, but there's probably a limit on how long you could run it for. There's also the possible "placebo effect" confound, which is a problem for both a controlled study and a twin study, but might be a bigger issue for the former (where participants are told to exercise) than the latter (where participants exercise or don't exercise of their own volition).

AstroChimpHam 12y ago

>But eventually the researchers homed in on 10 pairs of male identical twins, one of whom regularly exercised, while the other did not, usually because of work or family pressures, the researchers determined. That "work and family pressure" sounds like stress and a pretty important confounding variable.

reedlaw 12y ago
It's also a choice, or even an excuse. Nearly everyone has work and family pressures. Some find relief in exercise.
- maratd 12y ago
  > It's also a choice, or even an excuse. Alright, get off your high horse. Just because you "excercise" doesn't make you better. There are plenty who don't need to because they work with their hands and plenty more because they have active hobbies. And while it's a popular notion that constant activity makes you healthier, it's just common sense that the body is a machine and the more you stress a machine, the likelier it is to break. See athletes for common ailments.
  - samcal 12y ago
    > There are plenty who don't need to because they work with their hands and plenty more because they have active hobbies. And I bet those aren't the people about whom the parent was talking. It's not as if the benefits of exercise are unknown or controversial. Everyone knows that they are better off being active. Therefore, people who do not spend time being active are at the very least making a choice, if they legitimately have a more effective way of benefitting themselves, at most making excuses, if they do not have such a way.
  - omegaham 12y ago
    > See athletes for common ailments. This is a good point, and it's a good idea to pick a form of exercise that has less impact, (at an extreme end, I'm sure that the skiiers who do mogul racing are in great shape, but their knees probably don't work so well after a few years) but keep in mind that the body repairs itself. As long as you aren't repeatedly destroying your joints, you're going to get a lot of benefits from exercise. In many cases, athletes are less likely to get injured than the sedentary population because of increased strength and flexibility.

deleted 12y ago

[deleted]

gwern 12y ago

Fulltext: https://www.dropbox.com/s/gfch760k1ratwo3/2015-rottensteiner.pdf https://www.dropbox.com/s/gfch760k1ratwo3/2015-rottensteiner... / http://sci-hub.org/downloads/045f/10.0000@pdfs.journals.lww.com@generic-FD16BBD9129B.pdf http://sci-hub.org/downloads/045f/10.0000@pdfs.journals.lww.... Buried some interesting points there: > The researchers were looking for young adult identical twins in their early- to mid-20s whose exercise habits had substantially diverged after they had left their childhood homes. These twins were not easy to find. Most of the pairs had maintained remarkably similar exercise routines, despite living apart. Besides the testament to how 'everything is heritable' inherent in that observation, it also raises the question: if they are so unusual, doesn't that make confounding more plausible? > Interestingly, the twins tended to have very similar diets, whatever their workout routines, so food choices were unlikely to have contributed to health differences. Also very interesting, and counter to the usual narratives about health. (Everything is heritable...) > The twins’ brains also were unalike. The active twins had significantly more grey matter than the sedentary twins, especially in areas of the brain involved in motor control and coordination. Warning sign: 'significantly'. Does this mean, as any ordinary person would take it to mean (in conjunction with that lazy stock photo), 'a lot' or does it mean 'p<0.05'? Trick question, of course it means the latter, which is useless! Take a look at the fulltext, pg6, table 2, which spits out the actual differences between the twin pairs. I hope you're ready to be wowed by how much difference an exercise regimen makes when you control for genetics (picking out a few I recognize): 1. BMI: -0.8 2. VO2max: 6.3 3. weight: -2kg 4. waist circumference: -3.3cm 5. fat percentage: -3.3 (!) 6. lean mass: 1.4kg I'm not sure I've seen such a damning indictment of exercise in a long time. (Less than 1 on BMI? 2kg of weight? I fluctuate more than that on a weekly basis...)

lurknomore 12y ago
There are several sayings in fitness circles that are similar to this: "You can't outrun your fork." Diet is the primary reason people are obese, not lack of exercise.
- peteretep 12y ago
  I was about to post "can't outrun a fork" too. Hour of running five days a week burns only enough calories two account for two super-sized Big Mac meals.

bootload 12y ago

we can “move more,” surprisingly this is difficult, not impossible. Back in 2007 I did a simple experiment myself asking, 'at what point do you fail when repeating exercising?' The idea was pretty simple: pick a arbitrary impossible distance to cover and move each day to reach it. The impossible distance I chose 1000km in a year. So I selected a difficult 10km source and set out each day moving 10km per day until I complete my target. I reached my target by late November and decided to push-on to 1000Ml (1600Km), the last 400 in 20 days. The key failure point I found? Just before I started. If you could psychologically push through any excuse made not to go, just before you started, It's pretty likely you will start and finish. I keep this up averaging about 2000km/yr using that insight into failure. Up to 300km so far this year (with min/max 1kg weight and 8kg pack).

deleted 12y ago

[deleted]

mathattack 12y ago

"But eventually the researchers homed in on 10 pairs of male identical twins, one of whom regularly exercised, while the other did not, usually because of work or family pressures, the researchers determined." Oh boy... How can 10 possibly be enough?

laichzeit0 12y ago

I always find it interesting that whenever exercise/diet topics come up on HN that people will go to the n-th degree to try and discredit or rubbish the studies. Could it be a bias in the stereotypical geek which shuns both these habits and so seeks an intellectual reason to justify his sedentary lifestyle?

philjackson 12y ago
It's a cynical view, but I'm afraid to say I feel it too. This whole 'body acceptance' movement (in the context of obesity) that's happening at the moment is detrimental to society and should probably be shunned as overweight people justifying their inactive lifestyles.

parag_c_mehta 12y ago

Would have been great if some pictures were shared. Mere numbers do not tell full story that gets shown in actual pictures.

gadders 12y ago

From the report: "The scientists invited these twins into the lab and measured each young man’s endurance capacity, body composition and insulin sensitivity, to determine their fitness and metabolic health." Shame they couldn't find twins that took part in strength training, but not surprising given the difficulties in finding any participants.

Kiro 12y ago

> The active twins had significantly more grey matter than the sedentary twins, especially in areas of the brain involved in motor control and coordination. Is that good or bad?

pingou 12y ago
That looks good to me. What I'm wondering if that it only means that people have better motor control or coordination, or that it can also help people be good at math, for example, or at least help them if they decide to learn math?

darkhorn 12y ago

Can someone explain to me why an identical twin is allergic to mushrooms and the other one is not? Also why a symmetric identical twin is more friendly/outgoing and speaks fluently while the other one is opposite?

kristiandupont 12y ago
Without knowing any specific details, I can still answer that: because both allergies and personality are not (completely) dependent on nature, but to some extent on nurture.
jepper 12y ago
Because your immune system, a highly complex interaction between countless cells, is not fully determined just by your genes or your environment. There is also a stochastic factor.