Wednesday, January 03, 2007

That Post-Holiday Waistline Shall Not Trouble Your Sleep

This article is four years old (free registration required), and I have absolutely no idea why The New Republic decided to re-run it (on the front page of the Web site, no less), but it's still an enlightening read. It's comforting to think the science of health and nutrition has advanced beyond hype and mythology, but as this article shows, it's also sometimes wrong.
The most common way researchers determine whether someone is overweight is by using the "body mass index" (BMI), a simple and rather arbitrary mathematical formula that puts people of varying heights and weights on a single integrated scale. According to the government, you're "overweight" (that is, your weight becomes a significant health risk) if you have a BMI figure of 25 and "obese" (your weight becomes a major health risk) if your BMI is 30 or higher. A five-foot-four-inch woman is thus labeled "overweight" and "obese" at weights of 146 pounds and 175 pounds, respectively; a five-foot-ten-inch man crosses those thresholds at weights of 174 pounds and 210 pounds.
This is the catechism on our "obesity epidemic" -- your height and weight should align in some way that medicinicians have declared most healthy. It's conventional wisdom that everyone gets behind.
Yet, despite the intense campaign to place fat in the same category of public health hazards as smoking and drug abuse, there is in fact no medical basis for the government's BMI recommendations or the public health policies based on them. The most obvious flaw lies with the BMI itself, which is simply based on height and weight. The arbitrariness of these charts becomes clear as soon as one starts applying them to actual human beings. As The Wall Street Journal pointed out last July [this reference is as old as the rest of the article], taking the BMI charts seriously requires concluding that Brad Pitt, George Clooney, and Michael Jordan are all "overweight," and that Sylvester Stallone and baseball star Sammy Sosa are "obese." [...] To be sure, even if the BMI categories can be spectacularly wrong in cases such as those involving professional athletes, they're often a pretty good indicator of how "fat" most people are in everyday life. The real question is whether being fat--as determined by the BMI or by any other measure--is actually a health risk. To answer this question, it's necessary to examine the epidemiological evidence. Since the measurable factors that affect whether someone contracts any particular disease or condition can easily number in the hundreds or thousands, it's often difficult to distinguish meaningful data from random statistical noise. And, even where there are clear correlations, establishing cause and effect can be a complicated matter. If researchers observe that fat people are more prone to contract, say, heart disease than thin people, this fact by itself doesn't tell them whether being fat contributes to acquiring heart disease. It could easily be the case that some other factor or set of factors--i.e., being sedentary or eating junk food or dieting aggressively--contributes both to being fat and to contracting heart disease.
Okay, but this mostly sounds like common sense. What's the bottom line?
In a decided majority of studies, groups of people labeled "overweight" by current standards are found to have equal or lower mortality rates than groups of supposedly ideal-weight individuals. University of Virginia professor Glenn Gaesser has estimated that three-quarters of all medical studies on the effects of weight on health between 1945 and 1995 concluded either that "excess" weight had no effect on health or that it was actually beneficial. And again, this remains the case even before one begins to take into account complicating factors such as sedentary lifestyle, poor nutrition, dieting and diet drugs, etc. "As of 2002," Gaesser points out in his book Big Fat Lies, "there has not been a single study that has truly evaluated the effects of weight alone on health, which means that 'thinner is healthier' is not a fact but an unsubstantiated hypothesis for which there is a wealth of evidence that suggests the reverse."
This doesn't mean that being overweight suddenly makes you healthy. Most reasons for gaining weight -- compulsive eating, bad diet, sedentary lifestyle, fad-dieting followed by binging -- are themselves not good for your system and over time will very likely make you feel unwell. But the point of the article is that the sheer fact of exceeding a body mass index threshold has absolutely nothing to do with how "healthy" you are. So what makes for a healthy person?
Of course, in a culture as anti-fat as ours, the whole notion of people who are both fat and fit seems contradictory. Yet the research done by Blair and others indicates that our belief that fatness and fitness are in fundamental tension is based on myths, not science. "Fitness" in Blair's work isn't defined by weight or body-fat percentage but rather by cardiovascular and aerobic endurance, as measured by treadmill stress tests. And he has found that people don't need to be marathon runners to garner the immense health benefits that follow from maintaining good fitness levels. Blair's research shows that to move into the fitness category that offers most of the health benefits of being active, people need merely to engage in some combination of daily activities equivalent to going for a brisk half-hour walk. To move into the top fitness category requires a bit more--the daily equivalent of jogging for perhaps 25 minutes or walking briskly for close to an hour. (Our true public health scandal has nothing to do with fat and everything to do with the fact that 80 percent of the population is so inactive that it doesn't even achieve the former modest fitness standard.)
So if you want to get some of that cold, sterile, 1984-style beauty goodness that Celine Dion is pushing, go ahead: eat less, exercise more, get that liposuction you've always wondered about. Just don't let celebrities tell you you're going to die any sooner than they are. Because you're not.

Update: Sure enough, I hustle over to the New York Times site and right on the front page is a (more up-to-date) essay by three doctors about the "epidemic of diagnoses" plaguing the medical industry these days.

Americans live longer than ever, yet more of us are told we are sick.

How can this be? One reason is that we devote more resources to medical care than any other country. Some of this investment is productive, curing disease and alleviating suffering. But it also leads to more diagnoses, a trend that has become an epidemic.

This epidemic is a threat to your health. It has two distinct sources. One is the medicalization of everyday life. Most of us experience physical or emotional sensations we don’t like, and in the past, this was considered a part of life. Increasingly, however, such sensations are considered symptoms of disease.
This applies to things like sadness, occasional insomnia* and my favorite, a fake disease they call restless leg syndrome.
Two developments accelerate this process. First, advanced technology allows doctors to look really hard for things to be wrong. We can detect trace molecules in the blood. We can direct fiber-optic devices into every orifice. And CT scans, ultrasounds, M.R.I. and PET scans let doctors define subtle structural defects deep inside the body. These technologies make it possible to give a diagnosis to just about everybody: arthritis in people without joint pain, stomach damage in people without heartburn and prostate cancer in over a million people who, but for testing, would have lived as long without being a cancer patient.

Second, the rules are changing. Expert panels constantly expand what constitutes disease: thresholds for diagnosing diabetes, hypertension, osteoperosis and obesity have all fallen in the last few years. The criterion for normal cholesterol has dropped multiple times. With these changes, disease can now be diagnosed in more than half the population.
* - As opposed to my principled refusal to sleep. I just don't see the point. Rhubarb. Rghubarb. Rhourbab. Rhubaoyoyyrriy...........


Blogger charvakan said...

Good stuff. I've been lecturing people for years about the counterfactuality of the BMI craze. The people who live longest are those judged to be overweight, not those of "ideal" weight.

You're also right about the medicalization of everyday life. At my last visit to my doctor, he told me my blood pressure was too high (it averages 125/85--I give blood regularly so ti's measured often). I said, what gives, I thought the ideal was 120/80. He said that was the old standard--now if you're over 115/75 they want you on medication. He wanted to schedule another appointment to test it again and put me on drugs if it was high. I said it wasn't going to happen, so drop it. I lost some confidence in him that day.

7:31 PM  

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