exercise

The case against phys ed

pnrj education, ethics, personal , , , , , , , , ,

Dec 4 JDN 2459918

If I want to stop someone from engaging in an activity, what should I do? I could tell them it’s wrong, and if they believe me, that would work. But what if they don’t believe me? Or I could punish them for doing it, and as long as I can continue to do that reliably, that should deter them from doing it. But what happens after I remove the punishment?

If I really want to make someone not do something, the best way to accomplish that is to make them not want to do it. Make them dread doing it. Make them hate the very thought of it. And to accomplish that, a very efficient method would be to first force them to do it, but make that experience as miserable and humiliating is possible. Give them a wide variety of painful or outright traumatic experiences that are directly connected with the undesired activity, to carry with them for the rest of their life.

This is precisely what physical education does, with regard to exercise. Phys ed is basically optimized to make people hate exercise.

Oh, sure, some students enjoy phys ed. These are the students who are already athletic and fit, who already engage in regular exercise and enjoy doing so. They may enjoy phys ed, may even benefit a little from it—but they didn’t really need it in the first place.

The kids who need more physical activity are the kids who are obese, or have asthma, or suffer from various other disabilities that make exercising difficult and painful for them. And what does phys ed do to those kids? It makes them compete in front of their peers at various athletic tasks at which they will inevitably fail and be humiliated.

Even the kids who are otherwise healthy but just don’t get enough exercise will go into phys ed class at a disadvantage, and instead of being carefully trained to improve their skills and physical condition at their own level, they will be publicly shamed by their peers for their inferior performance.

I know this, because I was one of those kids. I have exercise-induced bronchoconstriction, a lung condition similar to asthma (actually there’s some debate as to whether it should be considered a form of asthma), in which intense aerobic exercise causes the airways of my lungs to become constricted and inflamed, making me unable to get enough air to continue.

It’s really quite remarkable I wasn’t diagnosed with this as a child; I actually once collapsed while running in gym class, and all they thought to do at the time was give me water and let me rest for the remainder of the class. Nobody thought to call the nurse. I was never put on a beta agonist or an inhaler. (In fact at one point I was put on a beta blocker for my migraines; I now understand why I felt so fatigued when taking it—it was literally the opposite of the drug my lungs needed.)

Actually it’s been a few years since I had an attack. This is of course partly due to me generally avoiding intense aerobic exercise; but even when I do get intense exercise, I rarely seem to get bronchoconstriction attacks. My working hypothesis is that the norepinephrine reuptake inhibition of my antidepressant acts like a beta agonist; both drugs mimic norepinephrine.

But as a child, I got such attacks quite frequently; and even when I didn’t, my overall athletic performance was always worse than most of the other kids. They knew it, I knew it, and while only a few actively tried to bully me for it, none of the others did anything to make me feel better. So gym class was always a humiliating and painful experience that I came to dread.

As a result, as soon as I got out of school and had my own autonomy in how to structure my own life, I basically avoided exercise whenever I could. Even knowing that it was good for me—really, exercise is ridiculously good for you; it honestly doesn’t even make sense to me how good it is for you—I could rarely get myself to actually go out and exercise. I certainly couldn’t do it with anyone else; sometimes, if I was very disciplined, I could manage to maintain an exercise routine by myself, as long as there was no one else there who could watch me, judge me, or compare themselves to me.

In fact, I’d probably have avoided exercise even more, had I not also had some more positive experiences with it outside of school. I trained in martial arts for a few years, getting almost to a black belt in tae kwon do; I quit precisely when it started becoming very competitive and thus began to feel humiliated again when I performed worse than others. Part of me wishes I had stuck with it long enough to actually get the black belt; but the rest of me knows that even if I’d managed it, I would have been miserable the whole time and it probably would have made me dread exercise even more.

The details of my story are of course individual to me; but the general pattern is disturbingly common. A kid does poorly in gym class, or even suffers painful attacks of whatever disabling condition they have, but nobody sees it as a medical problem; they just see the kid as weak and lazy. Or even if the adults are sympathetic, the other kids aren’t; they just see a peer who performed worse than them, and they have learned by various subtle (and not-so-subtle) cultural pressures that anyone who performs worse at a culturally-important task is worthy of being bullied and shunned.

Even outside the directly competitive environment of sports, the very structure of a phys ed class, where a large group of students are all expected to perform the same athletic tasks and can directly compare their performance against each other, invites this kind of competition. Kids can see, right in their faces, who is doing better and who is doing worse. And our culture is astonishingly bad at teaching children (or anyone else, for that matter) how to be sympathetic to others who perform worse. Worse performance is worse character. Being bad at running, jumping and climbing is just being bad.

Part of the problem is that school administrators seem to see physical education as a training and selection regimen for their sports programs. (In fact, some of them seem to see their entire school as existing to serve their sports programs.) Here is a UK government report bemoaning the fact that “only a minority of schools play competitive sport to a high level”, apparently not realizing that this is necessarily true because high-level sports performance is a relative concept. Only one team can win the championship each year. Only 10% of students will ever be in the top 10% of athletes. No matter what. Anything else is literally mathematically impossible. We do not live in Lake Wobegon; not all the children can be above average.

There are good phys ed programs out there. They have highly-trained instructors and they focus on matching tasks to a student’s own skill level, as well as actually educating them—teaching them about anatomy and physiology rather than just making them run laps. Actually the one phys ed class I took that I actually enjoyed was actually an anatomy and physiology class; we didn’t do any physical exercise in that class. But well-taught phys ed classes are clearly the exception, not the norm.

Of course, it could be that some students actually benefit from phys ed, perhaps even enough to offset the harms to people like me. (Though then the question should be asked whether phys ed should be compulsory for all students—if an intervention helps some and hurts others, maybe only give it to the ones it helps?) But I know very few people who actually described their experiences of phys ed class as positive ones. While many students describe their experiences of math class in similarly-negative terms (which is also a problem with how math classes are taught), I definitely do know people who actually enjoyed and did well in math class. Still, my sample is surely biased—it’s comprised of people similar to me, and I hated gym and loved math. So let’s look at the actual data.

Or rather, I’d like to, but there isn’t that much out there. The empirical literature on the effects of physical education is surprisingly limited.

A lot of analyses of physical education simply take as axiomatic that more phys ed means more exercise, and so they use the—overwhelming, unassailable—evidence that exercise is good to support an argument for more phys ed classes. But they never seem to stop and take a look at whether phys ed classes are actually making kids exercise more, particularly once those kids grow up and become adults.

In fact, the surprisingly weak correlations between higher physical activity and better mental health among adolescents (despite really strong correlations in adults) could be because exercise among adolescents is largely coerced via phys ed, and the misery of being coerced into physical humiliation counteracts any benefits that might have been obtained from increased exercise.

The best long-term longitudinal study I can find did show positive effects of phys ed on long-term health, though by a rather odd mechanism: Women exercised more as adults if they had phys ed in primary school, but men didn’t; they just smoked less. And this study was back in 1999, studying a cohort of adults who had phys ed quite a long time ago, when it was better funded.

The best experiment I can find actually testing whether phys ed programs work used a very carefully designed phys ed program with a lot of features that it would be really nice to have, but the vast majority of actual gym classes do not, including carefully structured activities with specific developmental goals, and, perhaps most importantly, children were taught to track and evaluate their own individual progress rather than evaluate themselves in comparison to others.

And even then, the effects are not all that large. The physical activity scores of the treatment group rose from 932 minutes per week to 1108 minutes per week for first-graders, and from 1212 to 1454 for second-graders. But the physical activity scores of the control group rose from 906 to 996 for first-graders, and 1105 to 1211 for second-graders. So of the 176 minutes per week gained by first-graders, 90 would have happened anyway. Likewise, of the 242 minutes per week gained by second-graders, 106 were not attributable to the treatment. Only about half of the gains were due to the intervention, and they amount to about a 10% increase in overall physical activity. It also seems a little odd to me that the control groups both started worse off than the experimental groups and both groups gained; it raises some doubts about the randomization.

The researchers also measured psychological effects, and these effects are even smaller and honestly a little weird. On a scale of “somatic anxiety” (basically, how bad do you feel about your body’s physical condition?), this well-designed phys ed program only reduced scores in the treatment group from 4.95 to 4.55 among first-graders, and from 4.50 to 4.10 among second-graders. Seeing as the scores for second-graders also fell in the control group from 4.63 to 4.45, only about half of the observed reduction—0.2 points on a 10-point scale—is really attributable to the treatment. And the really baffling part is that the measure of social anxiety actually fell more, which makes me wonder if they’re really measuring what they think they are.

Clearly, exercise is good. We should be trying to get people to exercise more. Actually, this is more important than almost anything else we could do for public health, with the possible exception of vaccinations. All of these campaigns trying to get kids to lose weight should be removed and replaced with programs to get them to exercise more, because losing weight doesn’t benefit health and exercising more does.

But I am not convinced that physical education as we know it actually makes people exercise more. In the short run, it forces kids to exercise, when there were surely ways to get kids to exercise that didn’t require such coercion; and in the long run, it gives them painful, even traumatic memories of exercise that make them not want to continue it once they get older. It’s too competitive, too one-size-fits-all. It doesn’t account for innate differences in athletic ability or match challenge levels to skill levels. It doesn’t help kids cope with having less ability, or even teach kids to be compassionate toward others with less ability than them.

And it makes kids miserable.

What do we mean by “obesity”?

pnrj development economics, public policy , , , , , , , , , , , , , , , , ,

Nov 25 JDN 2458448

I thought this topic would be particularly appropriate for the week of Thanksgiving, since as a matter of public ritual, this time every year, we eat too much and don’t get enough exercise.

No doubt you have heard the term “obesity epidemic”: It’s not just used by WebMD or mainstream news; it’s also used by the American Heart Association, the Center for Disease Control, the World Health Organization, and sometimes even published in peer-reviewed journal articles.

This is kind of weird, because the formal meaning of the term “epidemic” clearly does not apply here. I feel uncomfortable going against public health officials in what is clearly their area of expertise rather than my own, but everything I’ve ever read about the official definition of the word “epidemic” requires it to be an infectious disease. You can’t “catch” obesity. Hanging out with people who are obese may slightly raise your risk of obesity, but not in the way that hanging out with people with influenza gives you influenza. It’s not caused by bacteria or viruses. Eating food touched by a fat person won’t cause you to catch the fat. Therefore, whatever else it is, this is not an epidemic. (I guess sometimes we use the term more metaphorically, “an epidemic of bankruptcies” or an “epidemic of video game consumption”; but I feel like the WHO and CDC of all people should be more careful.)

Indeed, before we decide what exactly this is, I think we should first ask ourselves a deeper question: What do we mean by “obesity”?

The standard definition of “obesity” relies upon the body mass index (BMI), a very crude measure that simply takes your body mass and divides by the square of your height. It’s easy to measure, but that’s basically its only redeeming quality.

Anyone who has studied dimensional analysis should immediately see a problem here: That isn’t a unit of density. It’s a unit of… density-length? If you take the exact same individual and scale them up by 10%, their BMI will increase by 10%. Do we really intend to say that simply being larger makes you obese, for the exact same ratios of muscle, fat, and bone?

Because of this, the taller you are, the more likely your BMI is going to register as “obese”, holding constant your actual level of health and fitness. And worldwide, average height has been increasing. This isn’t enough to account for the entire trend in rising BMI, but it reduces it substantially; average height has increased by about 10% since the 1950s, which is enough to raise our average BMI by about 2 points of the 5-point observed increase.

And of course BMI doesn’t say anything about your actual ratios of fat and muscle; all it says is how many total kilograms are in your body. As a result, there is a systematic bias against athletes in the calculation of BMI—and any health measure that is biased against athletes is clearly doing something wrong. All those doctors telling us to exercise more may not realize it, but if we actually took their advice, our BMIs would very likely get higher, not lower—especially for men, especially for strength-building exercise.

It’s also quite clear that our standards for “healthy weight” are distorted by social norms. Feminists have been talking about this for years; most women will never look like supermodels no matter how much weight they lose—and eating disorders are much more dangerous than being even 50 pounds overweight. We’re starting to figure out that similar principles hold for men: A six-pack of abs doesn’t actually mean you’re healthy; it means you are dangerously depleted of fatty acids.

To compensate for this, it seems like the most sensible methodology would be to figure out empirically what sort of weight is most strongly correlated with good health and long lifespan—what BMI maximizes your expected QALY.

You might think that this is what public health officials did when defining what is currently categorized as “normal weight”—but you would be wrong. They used social norms and general intuition, and as a result, our standards for “normal weight” are systematically miscalibrated.

In fact, the empirical evidence is quite clear: The people with the highest expected QALY are those who are classified as “overweight”, with BMI between 25 and 30. Those of “normal weight” (20 to 25) fare slightly worse, followed by those classified as “obese class I” (30 to 35)—but we don’t actually see large effects until either “underweight” (18.5-20) or “obese class II” (35 to 40). And the really severe drops in life and health expectancy don’t happen until “obese class III” (>40); and we see the same severe drops at “very underweight” (<18.5).
With that in mind, consider that the global average BMI increased from 21.7 in men and 21.4 in women in 1975 to 24.2 in men and 24.4 in women in 2014. That is, the world average increased from the low end of “normal weight” which is actually too light, to the high end of “normal weight” which is probably optimal. The global prevalence of “morbid obesity”, the kind that actually has severely detrimental effects on health, is only 0.64% in men and 1.6% in men. Even including “severe obesity”, the kind that has a noticeable but not dramatic effect on health, is only 2.3% in men and 5.0% in women. That’s your epidemic? Reporting often says things like “2/3 of American adults are overweight or obese”; but all that “overweight” proportion should be utterly disregarded, since it is beneficial to health. The actual prevalence of obesity in the US—even including class I obesity which is not very harmful—is less than 40%.

If obesity were the health crisis it were made out to be, we should expect that global life expectancy is decreasing, or at the very least not increasing. On the contrary, it is rapidly increasing: In 1955, global life expectancy was only 55 years, while it is now over 70.

Worldwide, the countries with the highest obesity rates are those with the longest life expectancy, because both of these things are strongly correlated with high levels of economic development. But it may not just be that: Smoking reduces obesity while also reducing lifespan, and a lot of those countries with very high obesity (including the US) have very low rates of smoking.

There’s some evidence that within the set of rich, highly-developed countries, obesity rates are positively correlated with lower life expectancy, but these effects are much smaller than the effects of high development itself. Going from the highest obesity in the world (the US, of course) to the lowest among all highly-developed countries (Japan) requires reducing the obesity rate by 34 percentage points but only increases life expectancy by about 5 years. You’d get the same increase by raising overall economic development from the level of Turkey to the level of Greece, about 10 points on the 100-point HDI scale.

 

Now, am I saying that we should all be 400 pounds? No, there does come a point where excess weight is clearly detrimental to health. But this threshold is considerably higher than you have probably been led to believe. If you are 15 or 20 pounds “overweight” by what our society (or even your doctor!) tells you, you are probably actually at the optimal weight for your body type. If you are 30 or 40 pounds “overweight”, you may want to try to lose some weight, but don’t make yourself suffer to achieve it. Only if you are 50 pounds or more “overweight” should you really be considering drastic action. If you do try to lose weight, be realistic about your goal: Losing 5% to 10% of your initial weight is a roaring success.

There are also reasons to be particularly concerned about obesity and lack of exercise in children, which is why Michelle Obama’s “Let’s Move!” campaign was a good thing.

And yes, exercise more! Don’t do it to try to lose weight (exercise does not actually cause much weight loss). Just do it. Exercise has so many health benefits it’s honestly kind of ridiculous.

But why am I complaining about this, anyway? Even if we cause some people to worry more about eating less than is strictly necessary, what’s the harm in that? At least we’re getting people to exercise, and Thanksgiving was already ruined by politics anyway.

Well, here’s the thing: I don’t think this obesity panic is actually making us any less obese.

The United States is the most obese country in the world—and you can’t so much as call up Facebook or step into a subway car in the US without someone telling you that you’re too fat and you need to lose weight. The people who really are obese and may need medical help losing weight are the ones most likely to be publicly shamed and harassed for their weight—and there’s no evidence that this actually does anything to reduce their weight. People who experience shaming and harassment for their weight are actually less likely to achieve sustained weight loss.

Teenagers—both boys and girls—who are perceived to be “overweight” are at substantially elevated risk of depression and suicide. People who more fully internalize feelings of shame about their weight have higher blood pressure and higher triglicerides, though once you control for other factors the effect is not huge. There’s even evidence that fat shaming by medical professionals leads to worse treatment outcomes among obese patients.

If we want to actually reduce obesity—and this makes sense, at least for the upper-tail obesity of BMI above 35—then we should be looking at what sort of interventions are actually effective at doing that. Medicine has an important role to play of course, but I actually think economics might be stronger here (though I suppose I would, wouldn’t I?).

Number 1: Stop subsidizing meat and feed grains. There is now quite clear evidence that direct and indirect government subsidies for meat production are a contributing factor in our high fat consumption and thus high obesity rate, though obviously other factors matter too. If you’re worried about farmers, subsidize vegetables instead, or pay for active labor market programs that will train those farmers to work in new industries. This thing we do where we try to save the job instead of the worker is fundamentally idiotic and destructive. Jobs are supposed to be destroyed; that’s what technological improvement is. If you stop destroying jobs, you will stop economic growth.

Number 2: Restrict advertising of high-sugar, high-fat foods, especially to children. Food advertising is particularly effective, because it draws on such primal impulses, and children are particularly vulnerable (as the APA has publicly reported on, including specifically for food advertising). Corporations like McDonald’s and Kellogg’s know quite well what they’re doing when they advertise high-fat, high-sugar foods to kids and get them into the habit of eating them early.

Number 3: Find policies to promote exercise. Despite its small effects on weight loss, exercise has enormous effects on health. Indeed, the fact that people who successfully lose weight show long-term benefits even if they put the weight back on suggests to me that really what they gained was a habit of exercise. We need to find ways to integrate exercise into our daily lives more. The one big thing that our ancestors did do better than we do is constantly exercise—be it hunting, gathering, or farming. Standing desks and treadmill desks may seem weird, but there is evidence that they actually improve health. Right now they are quite expensive, so most people don’t buy them. If we subsidized them, they would be cheaper; if they were cheaper, more people would buy them; if more people bought them, they would seem less weird. Eventually, it could become normative to walk on a treadmill while you work and sitting might seem weird. Even a quite large subsidy could be worthwhile: say we had to spend $500 per person per year to buy every single adult a treadmill desk each year. That comes to about $80 billion per year, which is less than one fourth what we’re currently spending on diabetes or heart disease, so we’d break even if we simply managed to reduce those two conditions by 13%. Add in all the other benefits for depression, chronic pain, sleep, sexual function, and so on, and the quality of life improvement could be quite substantial.