Study proves it's not unhealthy to be overweight? Nah.

Researchers at the University of Manitoba have released a study on the relationship between body mass and health problems. Here's a typical mass-media report on the findings, headlined, "Overweight people don’t have bigger health problems, study finds."

It's an epidemiological study, which means researchers looked back at a bunch of historical data about people and then tried to draw associations between those people with certain characteristics or behaviors, and how they fared over time. Epidemiological studies are much cheaper and easier and usually quicker to do than almost any other type of study, and they seem impressive because they often involve large numbers of people. But they also are some of the least reliable studies, being typically plagued with just about every problem that a study can have, including confounders (what happens to people in the study may have little or nothing to do with the causes that are being looked at), confusion of cause and effect (what happens to people in the study may actually be causing the factors that are being studied, rather than being caused by them), unrepresentative samples (the people being studied may not be typical of the population we care about), trying to draw conclusions from small differences, and more. Most studies about the relationship between health and weight we hear about are epidemiological studies, and we've had ample evidence over time that these are some of the least reliable among generally unreliable epidemiological studies.

But there may be something else to worry about with the conclusions of this Manitoba study, something that makes me wonder if the findings are actually right--but not for the reasons implied in reports of the study. 

Last year I met with Oberlin College biologist Keith Tarvin, who studies foraging behavior in animals. Tarvin explained to me that throughout most of the animal kingdom, animals will generally put on excess weight when provided with plenty of calorie-rich food and not given any reason to be physically active, such as having to forage or hunt for food, or having to avoid predators. (Animals that need to keep weight down in order to survive are sometimes an exception--birds, for example, can't fly if they get too heavy.) Situations where animals lose weight, on the other hand, are usually associated with some pathological state or threat--as for example when fish keep weight off in order stay small to be less visible to and appealing to predators, or to slow their maturation in order to preserve fertility and lower energy needs during times of drought, extreme temperatures, food shortages or other environmental pressures.

In other words--and at this point I'm merely expressing a conjecture that came up in my chat with Tarvin---it may be that, weight-related health factors aside, having a stronger appetite is associated with being well-suited to the environment. Or to put it differently, keeping weight off when there is plenty of rich food around and no pressing reason to be physically active is, in a sense, a pathological state. Apply this theory to human society today--and at this point I'm degenerating into my own conjecture--and we might well predict that being overweight is associated with being, in some ways at least, healthier than those who keep weight off.

Does this mean we should stop worrying about being overweight? Absolutely not. To conclude as much would be confusing cause and effect. If this conjecture is right, it means that being overweight is in some ways an effect of being healthy; it doesn't mean that being overweight confers any health benefits. And in fact, the possible rightness of this conjecture should have no bearing whatsoever on the well-established fact that carrying excess fat is generally unhealthy, and that people improve their health and lower their health risks when they lose excess fat.

Even if it's true that people who are overweight are in many cases healthier in some ways than many people who are not overweight, these lucky overweight would still on average even further improve their health by losing the excess weight, and those who are not overweight would become less healthy by putting on excess weight. That doesn't mean that weight loss is a pathological state, even though it's usually associated with one in the animal kingdom. We should understand that the loss of excess weight is a good thing, even if, in a way, it is an unnatural thing in our society of plentiful, overly stimulating, calorie-dense food and sedentary lifestyles. That's why our goal should be, in effect, to change what's natural in our society--so that people are pushed by everything they see around them to avoiding excess weight, rather than being pushed to consume rich food and avoid physical activity as they are today.

To have even a decent chance of proving that losing excess weight will make you healthier--or to solidly prove just about any theory about the relationship between excess weight and health--we'd need a randomized controlled trial in which people are randomly assigned to either become fatter than they are, or lose weight, or maintain their weight. That trial is never going to happen, for what I hope are obvious reasons. And this brings us back to the problems with epidemiological studies like the one done in Manitoba. They rarely answer the questions we really want to ask. Instead, they give us answers that only raise more questions. There's nothing wrong with that--it's how science operates. We should be grateful scientists are conducting these studies, and appreciate the fact that they add to our knowledge base. But we should also be aware of the extreme limitations and qualifications that attach to the findings.

In the case of the Manitoba study, I think it's fair to say the study at best tells us little about the healthfulness of avoiding being overweight, and at worst is, at least in how it's being reported, extremely and even dangerously misleading. One of the biggest problems with the obesity crisis is the lack of awareness and motivation on the part of a sizable percentage of overweight people. When a study like this gets press claiming that being overweight seems to be as healthy as not being overweight, we take a big step backwards, and cause real damage that could in principle be measured in the loss of many years of life in the population, not to mention the drop in quality of life experienced on average by the overweight. I wish scientists and journalists would start taking these issues into account in their reports to journals and the mass media.

The Impact of an Obese Presidential Candidate--Chris Christie?--on the Obesity Crisis

New Jersey Governor Chris Christie continues to insist he won't seek the Republican nomination for the U.S. presidency, but many suggest he's likely to reconsider. I normally avoid commenting on any individual's weight issues, but I feel compelled to make an exception for Christie, who is obese, for two reasons. First, he's a high-profile public figure who seems to be at least flirting with those who want him to run for president, which in my opinion means he ought to expect to surrender all rights to privacy in virtually all aspects of his life, as have most governors, not to mention potential presidential candidates. Second, the president of the United States is a role model for tens of millions of people, perhaps especially including children. Anything the president does, or anything he or she is, is likely to affect the choices people make about themselves for years to come. And in this the choices relate to a serious crisis in public health.

Let me start off by saying that in no way do I have anything critical or negative to say about Christie with regard to his obesity. Obesity in general has become a major crisis for humankind, and for most individuals it is a disaster at least for health, and likely in other ways. But that doesn't mean that people who are obese have done anything wrong or inappropriate, or that there is anything deficient in their character or behavior, or that they should be given a hard time. I'd like to see most obese people motivated and encouraged to adopt healthier behaviors, and supported in their efforts to do so, both for their own sake and the sake of all us, since all of society feels the pain of the resulting high health-care costs, lowered productivity, and higher risks of obesity (given that it has been clearly proven that obese people raise the chances that the people around them will be obese, for a variety of reasons). But I'm strongly opposed to obese people being insulted or otherwise being given a hard time over obesity. Christie is no exception, public figure and role model or not. His weight doesn't in any way affect what I think about him as a person or politician.

However, I think it's fair and even necessary to speculate on the effect that having an obese president, or even candidate, could have on the public's battle with obesity. I see two obvious possibilities:

1) It makes the problem of obesity worse by allowing obese people to feel that there must not be much of a problem with obesity, since we have such an admirable public figure who is obese.

2) It would help millions to lose weight by calling more attention to the problems related to obesity and solutions available to fix it.

Which way would it go? I think it would depend on what the obese candidate or president said about obesity. If he or she talked about it openly as a struggle and discussed the benefits of and means for losing weight in a smart way--namely, through behavior change approaches--then I think this person could be the best thing that's happened to public health in a long time. If he or she refused to speak about it, or, even worse, insisted on explicitly passing obesity off as a non-problem, or made a comfortable joke of it, I think it would be a public health catastrophe.

I think there's reason to believe Christie would be the more helpful sort of candidate and president with regard to attitudes about obesity. He was one of the first and very few prominent Republicans to speak out in favor of Michelle Obama's anti-obesity campaign, defending it against widespread Republican criticism. In my opinion that makes for an excellent litmus test on this question. Ms. Obama's campaign is low-key but brilliant, hitting a real sweet spot in encouraging modest, gradual, comfortable, sustainable behavior change of the sort that could significantly improve the lifetime health of tens of millions of children. Most Republicans who have spoken out on it, meanwhile, have treated it like an evil conspiracy. It took courage and wisdom on Christie's part to go against that flow.

That Christie himself is obese wouldn't take away from any support he offers of efforts to do something sane about the public problem. Indeed, his own condition would likely add to the impact of any support he offered, and that would be true whether or not he himself is willing and able to substantially improve his health and health risks by losing some weight or speaking out on his own struggles. Were he to take those additional steps, of course, and become president, he could single-handedly become a hurricane of life-saving change in America.

One thing I can't make up my mind on is what the effect would likely be if an obese candidate or president advocated a less-sound approach to weight loss. I fear that having a president who proudly announced being on an ultra-low-fat or ultra-low-carb diet, or a fasting diet, or a drug-assisted diet, or who expressed an interest in bariatric surgery, might end up doing more harm than good. These just aren't safe and effective approaches to weight loss for most people over the long term, and embracing such an approach would lead many people to try them and end up regaining the weight, while distracting them from the behavioral approaches that can actually help over the long term. That potential damage, of course, would have to be weighed against the benefits of having a candidate or president who was at least willing to confront the problem of obesity and advocate taking action.

In any case, I truly hope voters don't make any candidate's excess weight a factor in their choices. But if we do elect a president who is obese, I hope he or she can at least on a public level become part of the solution to the obesity crisis, not the problem.


By the way, here's a video of some of the media coverage of Christie's weight vis a vis his candidacy:

Angry Responses to My Piece On Alternative Medicine

First of all, my deep apologies for not posting in so long. I'm going to get back to a regular schedule, I promise.

My long article on alternative medicine came out a few days ago in The Atlantic. In a nutshell, I explain why more and more doctors are recognizing that alternative medicine does a better job in some ways with many patients than mainstream medicine does--even though the core physical treatments of alternative medicine seem to rely mostly or entirely on the placebo effect. In particular, I make the case that alternative practitioners tend to invest more time and effort in helping patients adopt healthier lifestyles and attitudes than do mainstream doctors, and these changes are likely to do more for most people's health and wellness on average than mainstream treatments.

Not surprisingly, several prominent medical-science bloggers have gone ballistic at the suggestion that alternative medicine might have something going for it. Here's a brief list of links to some of the notable, highly critical responses to the article:

Steven Salzberg's response
Steven Novella's response
David Gorski's response
Matthew Herper's response

I responded at modest length to each of these posts in the comment sections under the posts (except for Salzberg's post to the Atlantic, where my response is on a separate page. Salzberg and Novella, both highly respected scientists (and Novella is a physician as well) known to be strongly opposed to alternative medicine, were interviewed by me at length for the article, and their viewpoints were, I think it's fair to say, well-represented in the article. (Neither has suggested otherwise.) I didn't interview Gorski, but mentioned him in passing in the piece. Gorski is a physician-scientist who must be among the angriest voices on the planet with regard to alternative medicine--he is the hardest-core of this group of hard-core anti-alternative-medicine warriors--and he went after me some months ago with regard to my Atlantic profile of John Ioannidis, the highly acclaimed physician-researcher who has found so many problems with published medical research. Herper is, I believe, a lowly journalist like myself.

I'd like to make some relatively broad comments about these mostly angry responses to my article. I'll start off by pointing out that while these folks imply (they of course don't come out and say so) that they are representing mainstream medicine and indeed all of science and perhaps all of Western thought, they are not. As my article makes clear, mainstream medicine has been slowly moving toward increasing acceptance of alternative medicine. Increasingly, Gorski and other hard-core opponents of alternative medicine are themselves gradually being pushed toward the fringes of medicine. (Gorski concedes as much in his post.) Whereas I found top physician-researchers happy to say good things about alternative medicine wherever I looked, including at some the most prestigious academic medical centers in the world--I wasn't even able to fit them all into the article--I had to work a bit to line up two highly respected, articulate scientists who were intensely opposed to it so I could fairly present that point of view in the article.

Don't take my word for it--go out and ask physicians you trust what they think of alternative medicine. Yes, many still object to it, and most have some concerns and hesitations about it (as do I), but I've found that most have come to accept to some extent the fact that some of their patients, for whatever reasons, seem to get some real benefits from it, and often with problems that seemed resistant to mainstream medicine. Why would a caring physician, or any scientist, find this fact so hard to take?

Some of the attacks on my article also attempt to paint me as an alternative-medicine "apologist." But what does that even mean? Am I imagined to attend meetings of my fellow apologists where we come up with our arguments together? Apparently I'm being assigned to some terrible camp for which I'm supposed to be judged, rather than for my actual argument. Are my attackers mainstream-medicine apologists? Do any of us have to stoop to name-calling to make our points? For the record, I've never had anything to do with alternative medicine in my entire life until I took on this article, either as a patient or a journalist, and I did my best to come into it with an open mind, and with no skin in the game. If I'm an apologist for this field, I'm an incidental one.

There are two main claims that underlie all the attacks on my article. They are: 1) Because physicians could in principle provide the sort of health-improving attention to patients that alternative practitioners by most accounts are today much more likely to provide, and because it is so difficult to clearly prove that alternative practitioners do in fact do a better job in this regard, it's wrong to say that alternative medicine offers any advantage in this regard.  And, 2), because alternative medicine incorporates core treatments that don't actually have the (implausible) direct physical effect claimed, but rather work by the placebo effect, alternative medicine is a fundamentally evil, anti-scientific entity (voodoo!), and therefore one must never suggest there is any aspect of alternative medicine that might be good.

I can only shrug at these notions. You'll either buy them or you won't. I don't, and most physicians don't, as far as I can tell.

Those two basic arguments underlie Gorski's particularly rabid rant, too. But if you read it, you'll quickly find yourself buried in a detailed, apparently point-by-point refutation of virtually everything I say in my article. He goes through the article paragraph by paragraph, sentence by sentence, finding in each the logical flaw, the fallacy, the error of argument. Do I compare A and B? Then I'm a fool because A and B are different! Do I contrast C and D? Then I'm a fool, because it's a false dichotomy! Do I assert a point about science? What do I know about science, I'm a journalist, and therefore a fool! Do I quote a Nobel Laureate? Then I'm a fool, because I'm arguing from authority! Do I point out a problem with mainstream medicine? Then, fool that I am, I'm setting up a straw man! Do I cite a study? Then I'm a fool, because that study was trash, or I've misinterpreted it, or it doesn't apply here! Do I say that randomized studies, the gold standard of medical science, can't really settle the question of whether alternative medicine might ultimately do a better job in some ways? Then I'm a fool, because any question can be settled with randomized trials, and in fact the studies have been done!

A brief aside about studies: There are hundreds of thousands of researchers whose careers depend on producing studies, so I'm not exaggerating when I say there is a study, and probably ten or 50 or 200 of them, for just about any reasonable question you could possibly think of, with results for each question pointing in every possible direction. And in medical science sooner or later someone manages to cobble together a version of study for each question that can be called a randomized study. When someone like Gorski sets out to prove a point, or (as is more often the case) trash someone else's, he'll point to one of these studies and cackle, QED! And when his opponent, if she is playing the same game, disses that study as junk and plunks down a different study that points in the opposite direction, Gorski will declare that study invalid in some way. And soon the two will be slapping studies down in front of each other and tearing them up like a violent game of crazy eights. I never go there. In fact, I would prefer to not quote studies at all in my articles for that reason, but editors strictly require it--I have never been able to win that argument. But I do so knowing the Gorskis out there will claim they can trump my study with their study, or howl at every point that isn't backed up by a study.

At this point, if I were anything like Gorski, I'd fire back by taking on every single point of his rant, and show why each is flawed, and why every one of my points should stand. I won't play that game, because it accomplishes nothing. (Well, I play it a little, but try to keep it short, and to assert a broader perspective.) There is no argument in the world that a Gorski can't tear apart point by point, and (you'll have to trust me on this) no tearing apart Gorski could produce that I couldn't in turn rip to shreds. You can see these sorts of mind-numbing, often semi-childish back and forths in many of Gorski's rants, since his targets do sometimes take the bait, and you can frequently see them play out in the comments underneath his posts, since he draws a crowd that loves playing this game.

The basic problem here is simply that of being unable to see the forest for the trees. Science by tradition endeavors to break down phenomena into their simplest component parts, and many scientists, and fans of science, become so enamored of this approach (which certainly has its benefits) that they are incapable of approaching anything any other way. I suspect this is why when Gorski enters an argument, he immediately atomizes. What he won't, and perhaps can't, do, is take a step back from the dueling studies and the logic errors and the flawed reasoning and the inappropriate comparisons, and instead look at the big picture objectively, and ask, What's really going on here? What might I be missing? Is there another way of looking at this? Does there seem to be some important, underlying truth that's being suggested here, a truth that may differ from the "truth" I've been clinging to, at least to some extent?

In the case of this subject, that shouldn't be hard to do. My point is incredibly simple. Our healthcare system has left physicians unable to lavish the time on patients needed to make patients feel fully cared for, or to invest time and resources in getting patients to adopt the healthy behaviors and attitudes that are so effective in lowering the risk of our most serious diseases and in relieving the pain and discomforts of many,  many disorders. (I'm not even really making a controversial point here--you can read much the same in the pages of the New England Journal of Medicine of the Journal of the American Medical Association.) Alternative medicine practitioners often focus on these approaches, and many patients indisputably report that they benefit from it. Why should we care at all about medical science if it isn't dedicated to making us feel more well? But the enemies of alternative medicine are so blinded by their disdain for the "voodoo" element of alternative medicine--the fact that its core treatments depend on the placebo effect, and have no plausible mechanism--that they refuse to give an inch on any aspect of alternative medicine. Never mind that this placebo effect has been shown to accomplish wonders with regard to how patients feel, or that many and probably most of the drugs that physicians prescribe also don't do much more than placebo for most patients, along with carrying a risk of horrific side effects. And again, you can look all that up in the medical journals.

What I've tried to do in my Atlantic article, and in most of my work these days, is raise questions in areas where people already think they know the answer, but may not. I try hard to resist the temptation to claim that everyone should simply embrace a different answer, but rather merely endeavor to show that there may be a different answer, or set of answers, that work, to some extent, in some situations, for some people. I want to provoke intelligent conversation on a subject where many or most people didn't think there was anything to discuss. I want to open closed doors. But the Gorskis of the world treat intellectual doors as if it is their sworn duty to keep them tightly latched shut. They claim they're defending science. I assure you they are not. Nothing more closely represents the spirit of science than open-mindedness and a determination to put biases aside and seek out the ways in which one might be wrong. Nothing is a bigger affront to the scientific spirit than to put all one's might into trashing all arguments and evidence that threatens a preferred point of view. I estimate I've interviewed over a thousand scientists in my career, and the great majority of them were perfectly willing to confess their doubts, their hesitations, their concerns with being wrong, the questions that haunt their work and beliefs. The scientists who never give an inch when confronted with opposition to their claims and beliefs, who react with bile and disdain, who tear apart and take no prisoners, are as far as I can tell outliers, and are easily and best ignored. They can blog to their hearts' content, and win a core of like-minded fans, but in the end they won't do much harm. They're noisy preachers to the choirs.

But here's the biggest point I'd like to make about the alternative-medicine debate: Don't take my word for it, don't take the word of the Nobel Laureate or the top scientists I quote, don't take the word of the alternative-medicine practitioners I quote, and please, please don't take Gorski's word for it. Go out and see for yourself. Talk to mainstream doctors, and alternative-medicine practitioners. Talk to people about their experiences with different types of treatments. Decide for yourself whether there isn't something interesting going on with alternative medicine, something that seems to provide real help to some patients who were let down in some way by mainstream medicine. We don't all have to agree on what exactly is going on here, or whether it is entirely a good thing. But I'll bet you won't end up thinking that, as Gorski and others assert, alternative medicine is a purely evil and harmful thing that must be crushed. But fair warning: You may end being called an alternative-medicine apologist. On the other hand, you'll be in good company.

The Same Old Diet and Exercise Advice?

My cover story on obesity is out in the February issue of Scientific American. You can see part of the article on the Scientific American website, but most of it is behind a pay wall. I'd love to find some way to make some of it available freely in some form online here, without undercutting Scientific American's interests. I'll see what I can work out. (Meanwhile, I see that a university has posted the full article here.)

The reader comments on the article (about 50 so far) are right there for all to see, though. They reflect a cacophony of opinions, most of them sounding rigidly held, about what has caused the obesity problem and what will make it go away. Needless to say, the Atkinites are out in force among the comments (and in blog posts about the article), lecturing everyone on how diet and exercise don't work, how everyone except them misunderstands physics and biology, how it's all carbs, carbs, carbs. They read one book by Gary Taubes (available in very long and very short versions), and they think they know more than most scientists do about metabolism and thermodynamics. Whatever the merits of the Atkins diet (and I don't think there are many for most people, nor do most scientists and physicians), the kind of disdainful, pompous, simplistic certainty mixed with gullibility and obliviousness that many Atkins fanatics endlessly spout about this highly complex subject has come to feel very tedious to me. They're welcome to their diet and their opinion, but I can only hope few would-be dieters are actually swayed by it. If you want to understand the Atkins claims, read Taubes, he's a smart guy. But before you buy the conclusions, go out and ask everyone you know how long they stuck with the Atkins diet and kept the weight off. Or just go ahead and try it (I did), but if it doesn't work for you long term, as it does not for the great majority of people (or me), please don't give up on diets. And I urge you not to give up on exercise as useless in fighting excess weight, as Atkinites suggest.

Some commenters try to dismiss the message of the article as the same old advice we've all been hearing forever about how we have to diet and exercise. That's an unfortunate point of view from several perspectives. First of all, the idea that advice should be dismissed because it's been consistently given for a long time is a troubling one. Not smoking, wearing seatbelts, drinking in moderation--this is the same old advice, too. You could argue, of course, that an article that focuses on the same old advice isn't very thrilling. What's much more entertaining is the latest and greatest breakthrough scientific finding about losing weight, or the latest diet guru's special claim on how to shed pounds with a simple change in diet. But it's the endless stream of claims for new approaches and insights that has pulled people away from what those experts who have achieved good results with the overweight have long known: you've got to focus on diet and exercise habits, and try to find ways to get people to take them up and stick to them forever. Part of the point of the article was to survey the scene and show how the same old basic advice, and not the endless stream of latest and greatest, is still what works, and what this means for the obesity crisis. What's more, the article points out prominently and at some length that there are indeed significant recent and ongoing improvements in our ability to help people stick to reasonable diets and exercise.

Yes, everyone has tried, and most have failed with, diet and exercise. But in spite of what many people believe (and some of the commenters imply) all diet and exercise approaches are not alike--far from it. A smart behavioral approach based on gradual, modest, livable changes that are strongly prompted and reinforced by others and by the environment is much, much more likely to succeed than the standard slash-calories-and-burn-up-the-treadmill plans most people subject themselves to, with predictable results. Very few people have embarked on a good behavioral program designed to bring on modest life-long lifestyle changes, rather than self-torturing in order to vaporize ten pounds in two weeks just so you can put them back on in the two weeks after.

Some people complain that I have some encouraging things to say about Weight Watchers. But the point I make in the article is that Weight Watchers is as close as most people ever get to a behavioral program, and that while it's better than most other mass-market programs and is based on sound principles, it doesn't come close in practice to being a full, state-of-the-art behavioral program that always stays true to those principles  And of course the great majority of overweight people and dieters haven't even tried Weight Watchers, never mind a genuine, full behavioral program.

Well, I hardly expected the article to instantly strip everyone of their misguided obsessions with  breakthrough findings and fad diets, and their distorted views of what behaviorism is about. My goal, as usual, was to try to promote discussion, and hopefully a slightly more informed, reasoned and open-minded one than one normally encounters, at least with regard to obesity and weight loss.

Of Baseball Pitches and Fad Diets: When science gets it wrong

An article by John Kay in The Financial Times (and thank you, TheBrowser.com, for highlighting it) recalls economics icon Milton Friedman's and a colleague's observation that we can often get very good at something (Friedman used billiards as an example) without knowing much about the complex principles behind it. I myself always appreciated the fact that physicists used to argue that a true curveball in baseball was an impossibility and that catching a fly ball required solving trigonometric equations, while baseball players (and in the latter case even dogs) effortlessly accomplish these feats without much regard for their impossibility or mathematical demands. And it will be a long time before our best scientists and engineers can design a fighter plane whose multi-computerized flight systems can begin to approach what a fly can do evasive-flight-wise with a teeny speck of a brain--a mere 100,000 neurons, or one-millionth as many as an aeronautical engineer. The prodigious pattern-recognition capabilities and other elegant programming of our brains endow us (and other creatures) with the ability to intuit or otherwise toss off solutions that elude formal analysis.

This notion that analytically daunting phenomena are often simply accomplished by other means brings to my mind some of the interchanges I've had in recent months with metabolic experts in both the ultra-low-carb and ultra-low-fat weight-loss camps. They've got the science theory, they've got the rodent studies, they've got the diet studies, and voilà: the only way to lose weight is cut out carbs or cut out fat, depending on which camp you're listening to. The two camps come to nearly opposite conclusions, and both are absolutely unwavering and uncompromising in their belief that the science completely and clearly proves they're right. And of course there are many other scientifically sure-of-themselves diet-gimmick camps.

Back in college my math and physics professors occasionally inflicted on me and my classmates a certain type of killer problem--well, they were killers to me, anyway--in which we were presented with a step-by-step proof that started with perfectly valid assumptions, and ended up with an indisputably mistaken conclusion. We had to figure out where the proof had gone wrong. I usually had a great deal of trouble doing so--the errors were very subtle, and sometimes were semi-errors spread out among several steps. These problems left me with a deep and permanent appreciation of how right something could look in every aspect of every step, and yet end up flat-out wrong.

Though scientists and other highly trained experts should know better--for one thing, I would think most of them got that same kind of what's-wrong-with-this-picture? problem in college--these folks often seem oblivious to the way that very right-sounding arguments can leave them impaled on silly conclusions. Of course, one of the main points of science is supposed to be to test theories to avoid this problem, but, as I've discussed endlessly elsewhere to the point where I'm tired of hearing myself repeat it (though fortunately others have been smartly chiming in on this subject lately) these tests tend to be terrible, and typically end up merely reflecting researchers' biases rather than getting at any real truths. In the end, the scientists who do the best work tend to be not the ones who avoid bias--that's just about impossible--but rather the ones who for whatever reasons end up with the right biases. When an expert's instincts run off the rails, you get, well, for example, claims that fat or that carbs are entirely responsible for obesity. And these experts become so convinced that the science and data back them up that their beliefs become unreasonably unshakable

This willingness of intelligent, knowledgeable people to let solid-seeming scientific reasoning make them absolutely certain about what is obviously not so is remarkable. There's so much easily observable evidence in the world all around us that people are able to lose weight and be healthy while still eating carbs, or still eating fat, that it just feels silly to have to make a point of arguing it--if someone doesn't see it at this point, they've just decided not to see it. Tens of millions of people have tried the Atkins-style ultra-low-carb diet--it was initially a fad diet in the 1970s, and was reignited as a much bigger fad in 2002 after a New York Times Magazine cover story outlined the science that seems to back it up, an article written by the brilliant science journalist (and my friend) Gary Taubes. Meanwhile, tens of millions more have tried very-low-fat diets. How has that worked out for America? We all know the sad answer to that question. Out of the dozen or so people I know personally who went on the Atkins diet, not a single, solitary one kept the weight off for more than two years, and most lasted on the order of a few months. (Some years back, after getting a very convincing science lecture one-on-one from Taubes, I tried it, and lasted three weeks--I felt like crap the whole time, though I don't seem to be typical.) I know a few people who lost weight on very-low-fat diets and actually kept it off, but they didn't really stick with the diet--they added back modest amounts of fats back in, and they also happen to be very physically active people.

Needless to say, what happens to my personal acquaintances hardly constitutes convincing evidence. But if you look at the range of diet studies out there and talk to a lot of experts in the field and others about what has and hasn't worked--something I've been doing quite a bit of for the past year--it becomes utterly clear that neither of these extreme diets achieves particularly good long-term adherence levels, and without long-term adherence a diet is at best a waste of time. To be sure, some people do permanently lose weight on one or the other approach, and in the Internet era a small minority of fad-diet beneficiaries can band together on websites and blogs and sound like a movement. More power to you if you're one of these beneficiaries. But clearly for the vast majority of people cutting out carbs or cutting out fat is simply not going be a lifelong habit. It doesn't matter whether cutting carbs or cutting fat will actually help you lose weight and be healthy--and it certainly doesn't matter if the science appears to back the approach up--if you can't stick with it. What we need, of course, is eating and exercise habits that we can stick with, and ways of being helped to adopt and stick with healthy eating and exercise habits. Cutting back at least a bit on carbs and/or fat is usually part of it, but it's not typically the main part, and it's rarely the entire shooting match. Having to drastically cut back on a major food group usually makes an eating plan nearly impossible to stick with long-term for most people. (But for those of you who insist on doing so, you might want to cover your bases with the Dukan Diet, a big fad diet in France that is now making its way to the US, and which advocates cutting out both fat and carbs, leaving you eating mostly protein. Good luck! In its defense, I'll point out that it does also advocate behavior-oriented measures. On the other hand, many medical experts caution that eating very-high-protein can be dangerous over the long term.)

I've tried talking to various advocates of extreme diets about these seemingly obvious problems with their claims and it's like talking to someone about deeply held religious beliefs. (Actually, some deeply religious people I've spoken with are much more open-minded about their beliefs than are some people who cling to dubious scientific beliefs.) Taubes is one of the smartest people I know, and he has surely become one of the most knowledgeable people on the planet with regard to how the human metabolism deals with sugar, but I just have to scratch my head over his (and his hard-core supporters') response to the observation that working on behavior change seems to be a critical factor when it comes to permanent weight loss, the response essentially being, "All eating-related behavior is driven by carbs and their effect on metabolism, exercise doesn't matter, the science proves all this, and that's that." Low-fat proponents, at least the ones I've interviewed, tend for whatever reasons to be much more aware of the role of behavior change than the somewhat fanatical very-low-carb crowd, but can be as tenacious in their patently implausible claim that a single type of food is largely responsible for obesity. Both low-fat and low-carb fanatics are of course very good at pointing out the holes in the scientific reasoning and evidence of the other camp, but blind to the holes in their own claims.

One of the things I really like about experts who focus on behavior change, and especially applied behavior analysis researchers--the folks who study ways of applying what is essentially B.F. Skinner's science of behaviorism--is that most of them rarely seem to get hung up on theories. They just try to figure out through observation of people what best works in real life--either for an individual, or for the greatest percentage of people in a group--and then that's what they push, while they continue to look for something that works even better, or on a broader range of people. It's very hard to picture a behaviorist insisting that a pitcher can't possibly make a baseball curve, or that eliminating carbs is a necessary and sufficient condition for shedding weight.