One Twin Exercises, the Other Doesn’t
well.blogs.nytimes.com
well.blogs.nytimes.com
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...)
Not sure if it's true, but it's at least as scientific as "can't outrun your fork".
I haven't bothered to check if there's scientific literature that proves ingesting calories is easier than burning them, but I think you'd struggle to find a scientist or sane person who doesn't feel that generally it's orders of magnitude easier.
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.
By the way, if anyone wants to attempt an unsupported hike of the John Muir trail, send me an email and I will be happy to give you some advice.
The first time I came to China, I didn't know how to find palatable food. (Yes, this was something I worried about beforehand.) Over the course of three months, I lost 15 pounds.
I had been variously described, before that point, as "thin", "stick-thin", and "skeletal".
When my dad picked me up at the airport afterwards, he was shocked. He said I looked like I was literally starving to death, which in a limited sense was true. I spent a lot of those three months visualizing pizza.
Was it the perfect diet? I'm sure the approach (just refuse to eat what's available) works. But it was a truly awful experience. Not recommended to anyone.
Your anecdotate is just a silly brag that adds nothing to the discussion.
With this interpretation, exercising and eating adequately are very strictly related, I'd say they have the same root.
But also from a more physical point of view, nutrition is also a function of exercise, since there are many needs of the body which are function of it. So it goes both ways, I wouldn't say one of them is primary.
> if they are so unusual, doesn't that make confounding
> more plausible
Example: You measure the effect of alcoholic beverages on general health. You create two groups, one group consists of the beer drinkers, another group gets the wine drinkers. Result: drinking wine correlates with better health, drinking beer does not. The confounding variable in this case would be class affiliation: working class members are more likely to drink beer than wine and are more probable to eat less healthy food and have less healthy jobs. By defining the groups solely by choice of beverage, the researchers have unwillingly split by the confounding variable of class affiliation.
His example was kids, schooling, and IQ; to 'control for' IQ you might try to compare kids with bad grades & high IQ with some other kids with good grades & high IQ, in order to find the effect of schooling on some outcome like crime. Except... kids with high IQ should have good grades; so why does that first group have bad grades? Why are they weird like that? What's going on? Do they have some sort of severe home problem? Emerging mental health issues? Systematic personality differences? You may well find that having 'controlled for' IQ, the kids with bad grades are more likely to be jailed and conclude that schooling helps prevent crime... but what have you really found?
In this case, what the researchers have found is that twins are powerfully locked together in terms of health outcomes, body types, diets, and exercise tolerance/preference, so locked together that they have to scour millions of people to turn up a handful of twin pairs. These twin pairs are 'matched' on genetics/upbringing (IQ), but not matched on exercise (grades), and so one gets health outcomes (jailing) 'controlling for' genetics/upbringing... so one concludes exercise helps prevent worse health... but what have you really found?
(At least, I think this is what Paul Meehl was talking about in http://www.mcps.umn.edu/assets/pdf/4.13_Meehl.pdf "Nuisance Variables and the Ex Post Facto Design", 1969, in _Minnesota studies in the philosophy of science: Vol. IV. Analyses of theories and methods of physics and psychology_ - that paper is unusually opaque for Meehl, and I'm not sure I understand it.)
That is a very good point.
> Also very interesting, and counter to the usual narratives about health. (Everything is heritable...)
And yet this need not lead us to the conclusion that self-improvement is futile. Consider the scenario where diet is highly heritable and also extremely important to health outcomes. If people could be convinced of the latter, they would, to varying degrees, improve their diet and therefore their health. After smoking was tied to lung cancer, I imagine that people (at all levels of genetic predisposition to smoking) greatly reduced the amount that they smoked. Smoking levels could have been 100% heritable both before and after the revelation, but would have been reduced over time.
> 5. fat percentage: -3.3 (!)
I'm not sure why you singled fat percentage out as the least significant (in the colloquial sense). The -3.3 is a reduction from 24.0, so the percentage change is ~14%.
> 2kg of weight? I fluctuate more than that on a weekly basis...
To take your quip seriously, I don't think this is a good comparison. If a specific intervention increased lean mass and decreased fat mass by equal amounts (say, 10kg), it would be highly beneficial and yet count for absolutely nothing with respect to BMI or weight. The specific changes cited here are 1.4kg lean mass and -3.3kg fat mass. I would actually count that as a 4.7kg improvement!
Finland Adult Obesity rate: 23%
America Adult Obesity rate: 35%When I quoted 2kg of weight, I meant '2kg of weight', not anything more complex. That's the total change. The exercising twins weigh 2kg less, total, all in all, on average. (If you think you've found a twisty interpretation of quoted figures which is more positive than it looks, please check the fulltext first - that's why I provided it!)
"the so-called active co-twin of the twin pair was physically active Q2 times per week, and the so-called inactive co-twin of the same pair, e2 times per month (inclusion criterion 1 is shown in Fig. 1). If this criterion was not met, the physically active cotwin needed to participate in leisure time physical activity Q2 times per week at an intensity equivalent to easy or brisk running"
No-one who is serious about training would expect any body composition changes from an easy run twice a week, except at the very lowest levels.
As others have said, "you can't out run your fork". If fat reduction is your goal, you have to get your diet in order. This is generally accepted within the fitness community, and it's a straightforward consequence that is trivial to consume more calories than you expend unless you're, say, trekking in the Arctic. If you want to increase your lean mass you'd better be doing resistance exercise twice a week at a minimum and more like three or four times as your training level increases.
What's wrong with that as a minimum cutoff level?
And if that's how people actually exercise, then the inefficacy is important to know. This reminds me of the arguments that 'communism has not failed, it's never been tried!' (Real exercise has not failed, it's never been tried by these twins...)
Seeing a significant change in three years is great. Imagine what it'll look like 10 years from now
> Besides the testament to how 'everything is heritable' inherent in that observation [...]
>> 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...)
Why do you think this proves genetic causes? They were twins, after all, they were both socialised under the exact same circumstances for two decades. Given they had identical upbringing, I'm not surprised that e.g. their preferences to food are quite similar.
It's important to remember, though, that correlations measured in twin studies, by design, only say something about the difference of both measured variable expressions, not about the variable itself. So if twin A has a BMI of 30 and twin B has a BMI of 35, that linked meta analysis says that heredity explains 75% of the difference between 30 and 35, or only 3.75 BMI points/ 10% of twin B's BMI in the given example. Even more interesting: The older the twins are, the smaller the difference gets (grep for 'decreased mean age' in the study).
If you weigh yourself at a controlled stage/time in your daily routine and fluctuate 2kg or more on a weekly basis, maybe you're doing something wrong.
Anecdata: I took up weight-lifting and running together and changed my diet. Presto changeo, over the past couple of years of doing this consistently I've lost about 12kg (EDIT: actually, no, that was in the single last February-February alone) while gaining lean muscle mass and gaining a few centimeters of height (that last part was sheer luck, of course). Oh, and my mood improved quite consistently, too.
Turned out being fat was mostly bad habits, with the problem being that I didn't think of them as alterable habits because I hadn't conceived of alternatives.
Want to lose weight, eat less and eat right
Want to look good, exercise and drink water
Somewhere down the line he stated that exercise tended to help you live longer and experience less issues as you grow up but it won't help you dodge that bus so enjoy yourself and don't get fat
However, the word "exercise" probably covers many different regimes here. If you take a pair of twins, put one on the couch for 3 years, and give me the other to train for 3 years with Starting Strength/Texas Method or similar, I will make him into an unstoppable monster in every dimension you can measure: Bone density, neuromuscular function, 1 rep max squat performance, bodyfat percentage, lean bodymass gained, whatever. He will even look conventionally "ripped" by the end of it if you let me control his diet a little bit. Same story if you subject him to the training regimen of an elite sprinter or something like that for 3 years.
If that same twin does Nautilus machine circuits for three years, he will probably be ~pretty much unchanged, depending on various genetic factors pertaining to sensitivity to light exercise.
Probably all of the options above would be colloquially called "exercise," but they're not even approximately created equal.
That "work and family pressure" sounds like stress and a pretty important confounding variable.
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.
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.
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.
The body is a biological organism, not a machine. Biological organisms that suffer disuse experience atrophy, wasting, and decay. Chronic controlled dosages of physical stress produce salutary effects in the human organism. Muscles grow and strengthen, bones increase in density, range of motion is preserved and increased, cardiovascular capacity increases, and even cognitive function is enhanced by exercise. You could not have summoned a worse analogy for the human body if it had been your intent.
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.
>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).
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.
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.
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.
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).
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.
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.
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).
This study may even be one of the ones that's unethical to do in a random fashion. We know that lack of exercise is bad for your health; telling people not to exercise for a year could be seen as doing active harm to study participants.
Of course, Twin Studies suffer from some issues on their own. I would prefer random-control tests where they're possible. But sometimes Twin Studies are all that you're going to get. And sometimes the Twin Study of an effect is the economic small-scale pilot that generates interest and funding for the "real" study, and there's nothing wrong with that.
There are ongoing debates around the degree to which obesity is a roll of the dice or not. Especially with the rise of Fat Acceptance-style lobby groups there is increasing pressure (alongside existing industrial sugar sellers like drink makers) to push back on the idea that a variety of health problems are obesity-related, or to tell people they need to change exercise/dietary habits.
In a way, it's quite impressive. They're doing much better than the pro-smoking lobby ever did, but it's also rather depressing from a public policy point of view.
As a corollary it's worth noting that if e.g. your workplace demands you work hours that effectively preclude you eating and exercising well there are substantial costs, not just for you, but for society more broadly.
That's what Fat Acceptance is fundamentally about. There's no subreddit exclusively for shitting on people who smoke or have bad posture. Nobody assumes that being dangerously underweight or not eating enough greens means that you're fundamentally lazy and lacking in willpower.
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.
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...
1) they'not simply comparing one that exercises with one that does not. They're comparing someone who needs exercising with someone who has the same need but can't anymore. But they would be wrong in assuming that everybody needs exercising as much as these twins do.
2) again, they're comparing couples of twins in which one keeps doing what he likes, so he's probably more happy and fulfilled, with another one who can't anymore, so is probably more stressed. Would the same work for golfing, singing or painting?
"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.
Oh boy... How can 10 possibly be enough?
Is that good or bad?
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?