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.
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.
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.
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.
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
banning all junk food and proscribing (sic) mandatory exercise to all overweight people and punishing noncompliance with fitness prisons.
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.
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.
amphetamines (extremely illegal, in amounts needed to fight obesity very safe)
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.
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
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.
I'm disappointed that he didn't say more about the specific public health policies that have been proposed. Policies like taxing junk food, making cities more walkable, requiring menu calorie labeling, and cutting corn subsidies all seem like they could make our society a little healthier and thinner, on the margin, without much of a cost. Instead of engaging with the question of whether these sorts of policies were good ideas, he incorporated the public health questions into his overarching narrative of the obesity panic. (See: Missing the Trees for the Forest)
If I were emperor I would ban scales from all homes (just kidding -- sort of)
What a horrible way to end a sentence!
The amount of irrationality surrounding the obesity topic is really absurd. This following is a good example:
http://www.jhsph.edu/publichealthnews/press_releases/2008/wang_obesity_projections
The article claims that by 2030 86% of Americans will be overweight. This is based purely on extrapolating the trends of the last 30 years. My own reading of the actual literature on the topic implies that a large minority of people are simply not weight-gainers. They have a lower appetite or have faster metabolisms or something other factor that protects them from weight gain. My understanding is that the rate of overweight has been increasing more slowly in recent years, as essentially all the people capable of becoming overweight already have.
Also, if obesity lowers life expectancy and causes serious health problems, I would expect people who are genetically more prone to obesity to have fewer descendants. I also suspect slimmer people probably reproduce more because 1. fitter men are more sexually successful and 2. pregnancy can be complicated by obesity. Since cheap, readily available fatty foods have only been available recently, the obese-prone have never been strongly selected against until now. Basically, fast food is kicking obese people out of the gene pool.
Also, if obesity lowers life expectancy and causes serious health problems, I would expect people who are genetically more prone to obesity to have fewer descendants.
This is a fun theory, but I don't think it, y'know, works. Not being in the African savanna anymore, "pregnancy can be complicated by obesity" seems unlikely to have a powerful long-term effect. The effect is small enough in the aggregate population that it will easily be washed out.
Basically, yes, the obese would have slightly fewer children, ceteris paribus, but in dealing with complex social factors, ceteris is almost never paribus.
The attractiveness idea is fascinating, but probably wrong. People tend to anchor. My google-fu is not refined enough to find the study, but, in speed dating, the number of callbacks remains fairly constant even as group composition varies. If, on a given night, men are shorter or women are heavier, the opposite gender changes their standards accordingly. Traits that reduce sexual attractiveness are bad for the individual, holding else constant. But if those traits affect a large number of individuals, they're largely irrelevant. Indeed, standards of attractiveness may even change a little; we're already seeing some backlash against the idea that super-skinny is sexy.
The main thing that determines how many kids people have is... get ready... how many kids they want to have and/or how careful they are to avoid having more than this number. The strongest macroscopic determinant of this is culture/class, which happens to also correlate with obesity.
Obese women 'significantly more likely to have children with birth defects' .
Women are getting more beautiful. "Beautiful women have more children than their plainer counterparts."
Taller men... are more likely to father children. Tall men are less likely to be obese. Not a direct correlation though. Tall men also tend to earn more.
Just some results that may help shed more light on this. Without better data I don't want to make any definitive statements, though.
Granted, but that particular claim is not especially relevant to this conversation, nor does Wikipedia's article on Kanazawa refute Jokela's findings. My purpose for linking to that wasn't to highlight the "women are getting more more beautiful" headline but simply to draw a connection from the claim that beautiful women reproduce more to the conclusion that obese women would therefore reproduce less. I don't back this claim, because I haven't read the paper, but unverified data is better than no data.
Having lived there and read up on problems with it, I find UK science reporting to be pretty awful, even compared to American science reporting.
The "birth defect" one is explained entirely in percentage change. Indeed, they are alarmed by the fact that deaths due to heart disease during pregnancy have doubled. They've doubled from .001% to .002% of all pregnancies. They don't even mention natural frequencies for birth defects, but they all sound rather rare.
The women are getting more beautiful thing is similar - it sounds more like the product of a scientist with good PR than a scientist with good data (note the tone of the article, as if women should be celebrating. But none of them are getting any more attractive; they are thoroughly done evolving.). Also, attractiveness is positional, so if more people are less attractive, those people's standards are likely to change to include one another. I can't access the gated article or I'd break down their "objective measurements of beauty," but BMI does not seem like a great proxy for beauty, particularly given the positional nature of the whole thing. And that researcher and his methodology have been criticized, for example here and here.
Height tends to correlate with both income and social class, which inversely correlate with obesity. Also note the article's failure to say how big an effect there is. Also note that tall men don't necessarily have more descendants, since taller women are less likely to have children, and (I'm pretty sure) taller men have taller daughters.
"There aren't any health differences to speak of for people between BMIs of about 20 and 35"
This is not true.
To me, the low-carbohydrate approach to the obesity problem has been a real eye-opener. I recommend the book from Gary Taubes, "Good calories, bad calories".
Reading that book i got clear that medical authorities have a very hard time updating their beliefs in the light of evidence, and prefer to surpress/bend it to accommodate established dogma.
fatness is a metaphor for poverty, lack of self-control, and other stuff that freaks out the new Puritans
My favorite recent example of this is the flash video The credit crisis visualized, which shows "subprime" borrowers as fat, tattooed smokers with (too) many kids, while the "prime" borrowers are none of those.
Very interesting. Oddly, I've never really questioned the idea that being fat is unhealthy, probably because you hear it so much from medical authorities like doctors and public health officials. I can't remember the last time I went to the doctor without being told to lose weight to improve health conditions I don't even have (but am at, supposedly, higher risk for).
Let's consider, though, why humans can become fat. The body stores energy in the form of fat for later conversion to sugars in the event of insufficient sugars to keep the body functioning. Sugar is only part of what the body needs to keep functioning (we also need amino acids we can't synthesize except by deconstructing muscle, trace amounts of vitamins and minerals, and water), but it seems to be the most critical since our bodies are very good at storing it. To me this suggests that outright starvation is, evolutionarily speaking, a far greater threat than lack of access to particular essential comestibles. So our bodies are doing the right thing by making us fat because it protects us against the very real and serious threat of starvation.
The problem is that, today, in the first world, we have little risk of starvation. Even a lack of money is no reason to starve: charities and governments feed the destitute. But our bodies don't know this, so they keep trying to put on fat. The result is that it's very easy for people to become overweight because an ability to easily store and retrieve sugars in the form of fat was an evolutionary win: it doesn't matter how fit you appear, if you don't have enough fat you'll be the first to die of starvation when there's not enough food. So we should expect the majority of the population to be "overweight" whenever there is sufficient food available, which is exactly the trend we see (the time of real plenty has been, sadly, only in the last few decades).
So why is thin beautiful? Historically being thin was not attractive, especially for women, as evidenced by human art that has long shown women with at least some significant fat stores as the most attractive. In the first world, though, since sometime between about 1960 and 1980, thin became attractive. The reason seems clear: the middle class and even the poor could now get fat thanks to low cost high quality food, and so the rich (and others with high status) must have, probably mostly unconsciously, switched to thinking thin beautiful in order to retain a clear signal of higher status, a situation with plenty of precedent (consider the pale/tan swap, the car/horse swap, etc.). So regardless of health concerns, real or not, thin is in because it's become a means of signaling status.
Given this, we should be highly suspicious of claims that we need to become thinner. It's not a conspiracy, but it certainly looks like the usual game humans play to display status. Since our doctors are, unfortunately, also only human, they too are playing the status game and consider thin beautiful, and so are tempted to rationalize reasons why people should be thin since they want to help people and believe that they will be better if they lose weight. It's a cruel twist that humans have a very hard time losing weight.
So, what's to be done? Probably nothing, although it's a worthy goal to push the elimination of weight as a status signal because even a partial success would result in a lot less suffering for billions of people. In the mean time, at least LW readers can eliminate from themselves false beliefs that anything but extreme obesity, or extreme skinniness, has anything more than a marginal health effect.
Let's consider, though, why humans can become fat. The body stores energy in the form of fat for later conversion to sugars in the event of insufficient sugars to keep the body functioning.
You know that mammals cannot convert fat to sugar no matter what, right? (OK, there's some limited evidence that glyoxylate cycle enzymes might be present in mammals, but even if they are active, what doesn't seem terribly likely, the primary way to utilize fatty acids is definitely beta oxidation, which burns them for ATP).
To me this suggests that outright starvation is, evolutionarily speaking, a far greater threat than lack of access to particular essential comestibles.
There's an argument that pre-agricultural food had a lot higher micronutrient to calorie ratio, so micronutrients were unlikely to be lacking even on very restricted diet. Modern food is supposedly selected for high calorie content.
Historically being thin was not attractive, especially for women, as evidenced by human art that has long shown women with at least some significant fat stores as the most attractive.
As far as I can tell most art shows women of healthy weight as attractive, very rarely overweight or obese kind.
Probably nothing, although it's a worthy goal to push the elimination of weight as a status signal because even a partial success would result in a lot less suffering for billions of people.
Why would we want to eliminate a status signal that's so easy to manipulate for smart people?
In the mean time, at least LW readers can eliminate from themselves false beliefs that anything but extreme obesity, or extreme skinniness, has anything more than a marginal health effect.
Metabolic syndrome seems real enough. Even if being moderately overweight wasn't a health risk, it seems likely that someone moderately overweight is much more likely to become morbidly obese than someone with healthy weight. And far more people suffer from obesity-related diseases now than ever - so even if it's mostly the extreme cases, if anti-fat interventions can get them to just moderately overweight it's obviously worth it.
You know that mammals cannot convert fat to sugar no matter what, right? (OK, there's some limited evidence that glyoxylate cycle enzymes might be present in mammals, but even if they are active, what doesn't seem terribly likely, the primary way to utilize fatty acids is definitely beta oxidation, which burns them for ATP).
I was unaware of this. I am woefully ignorant of many aspects of biochemistry, so this was described as I recall the process being described. If fat isn't converted back to sugars, I think it doesn't affect the argument too much because the point is still to convert fat into energy later.
As far as I can tell most art shows women of healthy weight as attractive, very rarely overweight or obese kind.
I can't find a handy reference, but I recall (from art history class) that women who were at least slightly overweight have long been portrayed as the ideal in art around the world. It may be necessary to consider that what's considered a healthy weight today may have looked slightly overweight (indicating good access to quality food, a signal of status) to artists in the past.
Why would we want to eliminate a status signal that's so easy to manipulate for smart people?
Because it's not easy to manipulate no matter how smart you are. If someone were so smart as to figure out a successful, lasting intervention, they'd be rich from selling the diet to the rest of us. Taking a page from Robin Hanson, there's a benefit to this similar to that of taxing the tall.
Because it's not easy to manipulate no matter how smart you are.
Fat is trivial to manipulate. I lost 27kg (BMI 30 to 22) without any effort with ECA (with non-junk diet and a light amounts of exercise, nothing unusual), it's stable for many years now. Just ask any bodybuilders for advice - they know how to do it, or read pubmed about ECA. The difficult part is not believing the popular culture's completely ineffective methods, once you do that losing your fat is trivial matter.
While that may work for you, things like ECA have significant side effects for many people, especially those who have already developed weight-related illnesses, and there are some people for whom they don't work. Given the effectiveness of the pharmaceutical industry in marketing medications, even non-prescription ones, the strong desires of millions of people to lose weight, and the length of time ECA products have been available, it seems unlikely that they are really as effective as you claim.
That's a ridiculously strong version of efficient (medical) market hypothesis. As I said, ECA is semi-legal in States, and its marketing for weight loss is not allowed by FDA. Also, as a non-patented drug, medical industry has absolutely zero incentive to advertise it.
As far as anecdotes go, so far one person on lesswrong tried ECA, and got back to me saying it didn't work. Turned out it was very low dosage ECA and on doubling it there were instant effects.
If you have weight problems, just go ahead, try it, and then tell me it didn't work. That will be unlikely.
Let's consider, though, why humans can become fat. The body stores energy in the form of fat for later conversion to sugars in the event of insufficient sugars to keep the body functioning. Sugar is only part of what the body needs to keep functioning (we also need amino acids we can't synthesize except by deconstructing muscle, trace amounts of vitamins and minerals, and water), but it seems to be the most critical since our bodies are very good at storing it. To me this suggests that outright starvation is, evolutionarily speaking, a far greater threat than lack of access to particular essential comestibles. So our bodies are doing the right thing by making us fat because it protects us against the very real and serious threat of starvation.
That is the standard argument. Maybe it is true. But has it actually been tested? Is it observed that when famine strikes, the fat survive best, or that people with a tendency to fat in times of plenty survive better than the naturally thin in conditions of chronic scarcity? A lot of things with obvious explanations turn out not to be true, and there's surely enough famine in the world to study.
After all, if the standard explanation is true, then we do know how people can make themselves thinner: eat as if food were in chronically short supply. This does not tell us how to make people thinner, short of concentration camp conditions, which certainly did work --- none of the liberated prisoners were fat. But outside of such extremes, making people do anything is difficult.
See also Intermittent Fasting (eat only every other day), reputed to also extend life.
Being fat is unhealthy because it does leave you more susceptible to disease. The American health care system wastes billions of dollars each year on diseases and conditions that are a direct cause of obesity. Diabetes, heart disease, high blood pressure, and cardiovascular disease are just a few of the conditions that could be completely avoided by millions of Americans if they just ate/exercised better. It seems that easy access to high calorie junk food and absolutely no exercise (never taking the stairs) is just too much of a temptation for many people... and in evolutionary speak, is a good indicator of that person's genes.
Obesity rarely occurs in nature because obese animals are targeted quickly by predators and quickly dispatched. The fat rabbit cannot escape the lean, muscular leopard chasing after it. In the event of a massive human starvation scenario I would argue that the fat people would be killed off first (possibly by the lean/muscular humans or predators) as the lean humans would require less resources and would be more capable of gathering food for the tribe. What good are obese/severely obese people in the hunter/gatherer world?
Think about all the benefits staying fit yields. It is easier to sit down, get up, row a boat, hunt for food, have sex, run, participate in sports, attract mates (good genes), defend your tribe, etc.
Obesity rarely occurs in nature because obese animals are targeted quickly by predators and quickly dispatched.
I would love to see evidence of this. I was under the impression that obesity is uncommon in the natural world because vast supplies of food are uncommon in the natural world.
Being fat is unhealthy because it does leave you more susceptible to disease.
That level of fat is not what I'm trying to address here. Many people are termed "fat" who are not so overweight as to actually correlate significantly with these diseases. I believe the data shows that exercise and genetic disposition, not weight, is more strongly correlated (sorry, no reference handy; feel free to prove me right or wrong on that). Many "fat" people are actually not at much of a health risk because they are in good shape, as you get at.
I would argue that the fat people would be killed off first
It depends on what kind of starvation scenario we're talking about here. In the ancestral environment, starvation would typically be the result of changes in weather patterns. From what I understand, much of Africa during human evolution was temperate or subtropical forest with increasing amounts of savannah (the appearance of which it is often argued motivated the move to bipedalism). In a savannah seasonal changes drastically change the environment, such that in dry months there would be far fewer food resources than during wet months. Dry months don't mean total starvation, but with fewer animals and fewer plants producing fruit or edible vegetative parts, the average daily caloric intake would have dropped. This is when fat reserves become important: fatten up in the wet months to help you make it through the dry months.
Total starvation scenarios don't typically appear until the development of agriculture, because crop failure in an agricultural society often spells doom, especially if a monoculture provides the bulk of the sustenance. Such scenarios are a relatively recent occurrence, evolutionarily speaking, so we should expect to see only a slight selection effect as a result. In those cases, depending on the society, I can see how physical fitness may lead to survival (you out-compete your neighbors for the local food supplies, cf. post-apocalyptic survival scenarios), although the existence of a class of elites or strong cultural taboos might give greater advantage to those with other qualities.
What good are obese/severely obese people in the hunter/gatherer world?
None, but it's a moot question because they don't exist except perhaps in a hunter-gatherer society that is sufficiently large to require the emergence of strong hierarchical governance, thus allowing a few elites who no longer have to work to become fat. Just as with most animals, hunter-gatherers simply don't have the opportunity to get fat.
The American health care system wastes billions of dollars each year on diseases and conditions that are a direct cause of obesity.
I assume you meant "a direct consequence of obesity". Here's a quote from the original interview that contradicts your claim:
Paul: The correlations between higher weight and greater health risk are weak except at statistical extremes. The extent to which those correlations are causal is poorly established. There is literally not a shred of evidence that turning fat people into thin people improves their health. And the reason there's no evidence is that there's no way to do it.
Now, if your point of view is informed, the right way forward in the argument would be producing citations.
Also, the part of your comment that deals with evolution seems confused to me. Hunter-gatherers don't get obese because they don't have access to cheap food, not because natural selection kills off obese people. If the latter were the case, modern people (who evolved from hunter-gatherers, after all) would have genetic safeguards against obesity.
Now, if your point of view is informed, the right way forward in the argument would be producing citations.
I am literally so baffled by the thesis presented above I can't bring myself to disagree with it because I must be missing something. I mean, within five minutes on Google I found five studies showing strong correlations between various measures of body fat and coronary heart disease:
If I was willing to give it an hour, I'm sure I could have found sixty of them, and I know there are many similar studies about type II diabetes, cerebrovascular disease, et cetera. Because many of these are prospective studies, they have a better ability to show causality than longitudinal studies (although still not perfect). And another five minutes on Google find me several interventional studies about how turning fat people into thin people improves their health:
So what exactly is the thesis? That all of these studies are flawed in the same way? That there's some vital causal step that's been left out? Surely the author must know about these, right?
I think the story goes like this: there are correlations between weight and health. There are disputes, but let us skip that and assume for the sake of argument that thin people live longer than fat people. The next question is whether this is causal. If a fat person makes a big effort and becomes thin, will he have a long life, just like a person who was thin to begin with?
We can fill in the details of what the experiment looks like. We start with 200 fatties who want to get thin, and a random assignment of 100 to the control group, who get the usual crap advice about diet and exercise. Since this doesn't work they remain fat. The others get special good advice about diet and exercise. They diet and exercise sucessfully and become thin. Then we wait.
Later (10 years? 20 years?) we follow up. Did the newly thin live longer? It is hard to be sure of the outcome in advance, the observed correlations do not guarantee it.
This is where Paul Campos jumps in a says "hey wait a minute, we cannot do that experiment because we do not have special good advice to hand out."
That is a controversial position, and the key issue seems to be the duration of follow up. Qutoing from How effective are traditional dietary and exercise interventions for weight loss?
Data from the scientific community indicate that a 15-wk diet or diet plus exercise program produces a weight loss of about 11 kg with a 60-80% maintenance after 1 yr. Although long-term follow-up data are meager, the data that do exist suggest almost complete relapse after 3-5 yr.
Think about planning the experiment that I sketched earlier. The key to getting a crisp, clear result is a ten or twenty year follow up measuring all-cause morbidity and mortality. The designer of the experiment needs to chose an intervention for the trial group, but the weight loss interventions that follow up five years later are reporting almost complete relapse for all interventions. So design of the experiment shudders to a halt.
There's another, related explanation, which is superstimuli. A lot of modern processed food is developed to maximize its taste impact. If there's a feedback between loop between good taste and higher consumption, widepsread and rising obesity may be the result of processed foods breaking this feedback by tasting too good. "Low-fat" may also exacerbate the problem, since fat helps signal satiety, so high-sugar, low-fat foods provide calories without curbing hunger much.
A genetic or evolutionary explanation seems unlikely because obesity is distributed non-randomly throughout society. It affects certain regions, subcultures, and classes very differently. This could be partly explained by the tendency (via affluence, culture, whatever) of certain groups to avoid eating highly processed high-calorie foods. It may be explained simply by net calorie consumption, but I'd be surprised if that itself is not correlated with the consumption of high-calorie processed foods.
It seems fairly obvious that you're right about why humans become fat -- i.e., because in our evolutionary past, it was adaptive to do so when there was a lot of food around -- but I don't see how you get from that point to "doctors are ... playing the status game and consider thin beautiful" rather than "medical research has shown that obese people are at a higher risk from certain health problems". It's perfectly possible, and seems quite probable, that gaining weight is adaptive only a) up to a certain point, which was extremely rarely reached until recently, and/or b) under the actual conditions it was adaptive to -- that is, when the weight is highly likely to come off again during a period of famine.
Perhaps I should have split this into two comments, then maybe it wouldn't have gotten downvoted so far. Oh well, live and learn.
Yes, I agree that gaining weight is adaptive only up to a certain point, in part because in the ancestral environment there was not opportunity to get excessively fat. And I don't deny that putting on extra weight is not really necessary in the first world. But having and maintaining a BMI in the "overweight" range does not appear to be dangerous and is arguably the body's ideal state, since having less fat stores would be a real disadvantage.
I am probably guilty of making some too-big jumps in my reasoning to explain why fat is currently looked down on. I'm not entirely sure where they are, though, so if there's any points in particular that need explanation let me know. Maybe we'll find a flaw in my reasoning that I didn't expect to be there in the details.
Related To: The Unfinished Mystery of the Shangri-La Diet and Missed Distinctions
Megan McArdles blogs an interview with Paul Campos, author of The Obesity Myth. I'll let anyone who is interest read the whole thing, but here's some interesting excerpts:
I mean, there's no better established empirical proposition in medical science that we don't know how to make people thinner. But apparently this proposition is too disturbing to consider, even though it's about as well established as that cigarettes cause lung cancer. So all these proposals about improving public health by making people thinner are completely crazy. They are as non-sensical as anything being proposed by public officials in our culture right now, which is saying something.
It's conceivable that through some massive policy interventions you might be able to reduce the population's average BMI from 27 to 25 or something like that. But what would be the point? There aren't any health differences to speak of for people between BMIs of about 20 and 35, so undertaking the public health equivalent of the Apollo program to reduce the populace's average BMI by a unit or two (and again I will emphasize that we don't actually know if we could do even that) is an incredible waste of public health resources
and
Megan: An economist recently pointed out that we don't encourage people to move to the country, even though rural people live more than three years longer than urban people, and the diffefence in their healthy life expectancy is even more outsized. Nor do we encourage people to find Jesus or get married. We target "unhealthy" behaviors that are already stigmatized.
Paul: Right, as Mary Douglas the anthropologist has pointed out, we focus on risks not on the basis of "rational" cost-benefit analysis, but because of the symbolic work focusing on those risks does -- most particularly signalling disapproval of certain groups and behaviors. In this culture fatness is a metaphor for poverty, lack of self-control, and other stuff that freaks out the new Puritans all across the ideological spectrum, which is why the war on fat is so ferocious -- it appeals very strongly to both the right and the left, for related if different reasons.