
One Twin Exercises, the Other Doesn’t - igonvalue
http://well.blogs.nytimes.com/2015/03/04/one-twin-exercises-the-other-doesnt/
======
gwern
Fulltext:
[https://www.dropbox.com/s/gfch760k1ratwo3/2015-rottensteiner...](https://www.dropbox.com/s/gfch760k1ratwo3/2015-rottensteiner.pdf)
/ [http://sci-
hub.org/downloads/045f/10.0000@pdfs.journals.lww....](http://sci-
hub.org/downloads/045f/10.0000@pdfs.journals.lww.com@generic-FD16BBD9129B.pdf)

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
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.

~~~
WildUtah
"You can't outrun your fork."

I can.

People who can't outrun their forks aren't running hard enough.

Hunting down a lot of calories and eating them is part of being a mammal. I
bicycled across North America one fall on a mostly mountain route. Four times
a day I ate full meals and added as many Dove bars as I could without being
sick in between. I biked up and down hills with 30kg of gear all day. And I
lost a lot of weight.

Sure it hurts to work that hard, but it's supposed to hurt a little. Being
comfortable all the time isn't part of being a mammal.

~~~
rtb
I look forward to your enlightening anecdote based debunking of other sayings,
such as that time you made a great broth despite too many cooks, or that time
a gathering didn't get merrier with more people.

~~~
WildUtah
I'm a little too busy to entertain you with vignettes right now; I need to
supervise this pot closely until it boils.

------
AstroChimpHam
>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
It's also a choice, or even an excuse. Nearly everyone has work and family
pressures. Some find relief in exercise.

~~~
maratd
> 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.

~~~
runamok
> it's just common sense that the body is a machine and the more you stress a
> machine, the likelier it is to break

Except a biological system gets stronger if you stress it in a progressive
manner. While athletes constantly pushing themselves certainly do get injured,
doing nothing seems to cause far more harm long term. Everything from heart
health to bone density is usually better in an athlete.

Almost everyone in my family is obese with a host of maladies. I've been
running 23 years and am incredibly healthy despite the occasional hamstring
pull or achilles tendonitis.

------
probono1
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.

~~~
tghw
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
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.

------
bootload
_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).

------
Timothee
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
what's interesting is that this comparison controls for genetics, given that
they're twins.

~~~
Timothee
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
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.

------
laichzeit0
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
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.

------
darkhorn
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?

~~~
jepper
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.

------
Udik
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
Whats your point here, motivation is necessary to realize benefits from
training? And the absence causes body fat to accumulate?

~~~
bsder
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
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...

------
gadders
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.

------
mathattack
"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?

------
Kiro
> 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
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?

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

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

~~~
jostmey
Is that an actual picture of the twins?

~~~
kafene
My guess is that that's a picture from the art department.

~~~
alecdbrooks
It's attributed to Getty Images, so it's actually a stock photo.

