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Jonathan_Graehl comments on The Obesity Myth - Less Wrong
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Comments (59)
A small movement of the average (27 to 25) could consist of 1/5 of the population losing 10 points, rather than everyone losing 2 points. So quite a few people could have their health improved, even granting the unsourced 20-35 BMI iso-health range. Terrible reasoning.
As for the second point, encouraging people to get married (or Jesus) because of a correlation is very cargo-cult. At least with rural living, there's some credible mechanism for health-improvement (reduction in air and noise pollution). I'm sympathetic to the general theme: that the health advocacy I hear is filtered and biased, but I'd like some evidence of taboo health-suggestions that are at least as effective as popular ones.
I don't see why it matters if everyone who's overweight loses 2 points or if a fifth of them each lose 10 points. Instead of having one person cut their BMI from 40 to 30, we could have one person go from 40 to 38, another from 38 to 36, ..., and a fifth from 32 to 30. None of them will feel like they accomplished much, but the overall public health benefit will be the same.
The one way that unequal weight losses could be better would be if people who benefit more from losing weight (which would presumably be the people who are the most overweight) tend to lose more than other people. That seems like a plausible outcome for some policies (like junk food taxes), but with other policies (like subsidies on gym memberships) you might get the opposite.
Assume that BMI is actually useful. Then, assume everyone below median dropped 2 BMI points, and everyone above median stayed the same. This would lower the mean without having positive health effects (it might even have negative health effects). If you flip it, so the above-median lose weight, it'd have more positive health effects despite yielding the same mean. The overall public health benefit is simply not determined by the average effect, because 1 unit of BMI != 1 unit of harm.
If most of the harm comes from the extreme end (e.g. BMI 35+), then having the top 10% drop 10 points would alleviate a lot more harm than having everyone drop 1 point, even if the effect on average is identical. On the other hand, change among the people who are most severely overweight seems less likely to actually happen than slight change across the whole population.
I agree that it matters who is losing the weight (that is, where in the BMI distribution they are). That's the point I was trying to make in my 2nd paragraph. But it doesn't matter what increment they're losing the weight in. It makes almost no difference if a group of people all lose 2 points of BMI or if a randomly selected half of that group all lose 4 points.
If I'm reading them correctly, Paul Campos suggested that a 2 point drop in BMI was too small to make a difference, and Jonathan Graehl responded that a 2 point average drop in BMI could be big enough to matter if it results from some people having a much larger drop (which is big enough to make a difference) and others not dropping at all. My response was that any drop in BMI helps at the margin (as long as it happens to someone who is unhealthily overweight), and in the aggregate a lot of people each losing a tiny amount of weight can be just as good for public health as a smaller number of people each losing a substantial amount of weight. All that matters (if we pretend that health is solely a function of BMI) is the distribution of BMIs in the population beforehand and the distribution afterwards; it doesn't matter which individuals are responsible for the shift in the distribution.
I believe that "encouraging people to get married (or Jesus)" was said sarcastically. There were a couple times he used sarcasm that didn't really come through in the text, but could only be figured out be rereading and considering what message he was trying to convey.
I don't think it was sarcasm - religion and marriage are both strongly correlated with health.
But which is more likely to actually happen? Or, more realistically, which is less tremendously unlikely?
That depends on how exactly they tackle the problem. I can imagine an overwhelming force solution of banning all junk food and proscribing mandatory exercise to all overweight people and punishing noncompliance with fitness prisons.
I can imagine a miracle drug that makes your body shape and size easier to change than your hairstyle. That seems roughly as likely as
in a liberal democracy with a lot of overweight people and a massive food and agriculture lobby.
Actually there are already drugs that do a pretty good job of reducing body fat (even in people that are obese). The catch is that all of them are illegal, even the ones that can be used safely for the majority of people.
Such as...?
That's an enormous claim to make; I think it's fair to say such a claim should be accompanied by some kind of evidence, as I seriously doubt it's common knowledge if true.
Such as fen-phen (made illegal for absolutely no reason whatsoever, very safe), ECA (semi-legal depending on where you live, I wouldn't be surprised if it got delegalized completely at some point for no reason whatsoever, very safe), amphetamines (extremely illegal, in amounts needed to fight obesity very safe).
ECA in particular has enormous amount of research behind it, freely available on pubmed.
Unless you know the right lies.
Olestra (not a drug, but a chemical solution to part of the obesity problem) had a lot of promise. It didn't get banned, but people did freak out about a generally minor side effect, hold a health scare, and finally send it into commercial oblivion.
We have one of those. As a bonus, it gives you larger breasts (irrespective of sex), saves on contraceptives (fertility? hah!) and even makes changing your hairstyle easier (if you're going to need a wig anyway...)
That's pretty much the plot of Fat by Rob Grant, which contains some very good information on obesity and various other food-related health myths: one of the facts that stuck with me is the obvious-in-hindsight observation that (even in first world countries) it is massively more dangerous for your health to be underweight than to be overweight.
And both are massively more dangerous than being fit.
Well, yes, by definition, since we're pretty much using underweight to mean 'having a weight low enough to damage your health' and overweight in a similar manner: I'm not sure what your comment is meant to add.