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Screening for Obesity: Weighed, Measured, and Found Wanting

The updated advice from the Preventive Services Task Force about obesity screening harbors good, bad, and a bit of the downright silly.
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The United States Preventive Services Task Force, applying its reliably evidence-based and measured approach, has weighed in anew on weighing and measuring adults, and decided it's an even better idea than it used to be. The task force recommended specifically that clinicians screen all adults for obesity using the body-mass index, and refer those affected to intensive diet and exercise programs. This revised recommendation is directionally quite consistent with the prior guidance provided in 2003, but is a bit more specific and rather more emphatic.

I am a consistent proponent of the task force, which conducts rigorous reviews of evidence and reaches conclusions accordingly. The group is highly professional, multidisciplinary, and unencumbered by pertinent biases. They tell it like it is -- whether people want to hear it or not. They have received most widespread attention for making politically unpopular decisions about cancer screening that are nonetheless right given what we know.

The task force does what it does extremely well -- but what it does is advise about "from now on" based on "heretofore." They guide us about going forward by looking back, and are thus bounded and limited by what we already know. They are not about the way things should be. For those of us who embrace the spirit of "the best way to predict the future is to create it," task force recommendations can feel a bit like yesterday's news -- which, of course, is what they are based on. Yesterday's evidence, to be exact.

Another important limitation is that absence of evidence is not the same as evidence of absence -- but both forestall favorable task force recommendations. Absence of evidence may simply mean that science has yet to validate what sense emphatically suggests. It may mean there is no dedicated deep pocket to embrace the cause, as pharmaceutical companies embrace the cause of getting their new drugs approved -- as lorcaserin was approved for weight loss yesterday.

So while the work of the task force is reliably excellent, it represents a view of the world through one rather small window. Looking at a broader expanse of the relevant landscape, the updated advice about obesity screening harbors good, bad, and a bit of the downright silly.

The good here is that task force recommendations, even updates, garner media attention as this one has -- so more attention is being directed to the persistently urgent matter of hyperendemic obesity. Also good is the implication that since 2003, evidence has accrued that well-designed behavioral programs can, in fact, effectively treat obesity. That evidence is apt to be even better than indicated in this report, as there is a bit of a time-lag between the rigors of evidence review and the release of a recommendation. Two very compelling studies of Weight Watchers, for example, both published within the past year (October 2011; November 2011), suggest decisive benefits of just the kind of referral the task force is now recommending, but neither of these papers is cited in the report.

So the case the task force is making -- that we have behavioral interventions that can work -- is good news. And the actual news on that front, when brought fully up to date, is in fact better still.

Deferring the bad for the moment, we may concede that there is something of the "much ado about nothing" variety that makes obesity screening, and formal recommendations to that end, rather silly. For starters, formalizing the identification of obesity through screening, while technically valid, is a bit like formalizing the identification of baldness with a protocol to scrutinize the scalp. The reality is -- and we all know this already -- you have a pretty good inkling from across the room.

Unlike most of what we "screen" for in medicine, obesity, like baldness, may be willfully covered over, but is anything but invisible. There are, in fact, studies indicating that the "eyeball" test generally corresponds quite well with high-tech measures of adiposity. We can all tell from across a room not only if someone is lean or heavy, but if they are heavy from an excess of fat or muscle.

But more important than that is the prevalence of obesity. The CDC has recently suggested that current trends will carry us to an obesity prevalence of 42 percent among adults in less than two decades. Other researchers have suggested that by mid-century, essentially all American adults, but for a rounding error, will be overweight or obese. With such trends in mind, "screening" for obesity is somewhat analogous to screening for wet feet on the Titanic. It would make a whole lot more sense to assume that everyone's feet either already are wet, or are very likely to get that way unless some robust action is taken.

And, by the way, there is precedent for skipping over screening altogether and delivering a form of preventive treatment to all: dental care. In the absence of fluoride and routine dental cleanings, we are all at risk of caries (cavities). So routine dental care, rather than screening, is the standard of practice. Something similar for obesity is warranted on the basis of prevalence -- but awaits evidence that we have something universally effective to offer.

Which brings us back to bad. There is some bad in the task force report, through no particular fault of the task force, which merely did the job with which it was charged.

It is rather bad to need to go looking for a condition apt to develop in just about everybody before doing something about it. It is also bad to presume that doctors looking for, and reacting to, obesity will reliably do so constructively.

That thinking drives reimbursement, which thus far shows signs of compensating only those least qualified to do the job, with inattention to effective commercial programs, dietitians, and other resources of established merit. But worse, it invites clinicians with no relevant aptitude to wade into a dialogue fraught with real hazard. I have met the patients brutalized by colleagues with a "blame the victim" attitude about obesity, and I shudder to think their ranks might grow. (For my friends in the "personal responsibility" camp, I hasten to add: (1) You can share in responsibility for a solution without being to blame for the problem! (2) Taking responsibility requires being suitably empowered to do so; and (3) weight is an outcome, not a behavior, and nobody "chooses" what to weigh.)

And perhaps even worse than this is the potential to think that if clinicians are screening for obesity, it is a problem best tackled in the clinical realm. This, of course, is nonsense. The metabolic complications of obesity can and often do evolve into bona fide clinical problems. But obesity itself is a society-wide problem, all about feet and forks and the daily influences on them -- not stethoscopes, scalpels, and scans. It is medical hubris to think that solving the problem of population-wide obesity will owe much to clinicians reacting to it once it has developed in individual patients. The more emphasis we place on the modest contribution clinicians can (and should) make to a comprehensive solution, the more we risk failing to recognize and address the full scope of the problem.

And so, I support obesity screening on the basic merits of the limited and contextual evidence the task force reviewed. But when physician screening for obesity is weighed and measured against the backdrop of an obesigenic environment and the emotional toll of obesity on many patients, the practice has limited potential to do good; some clear potential to do bad; and as an exercise in searching for the common and fairly obvious, an inevitable patina of the just plain silly. As a society, it certainly leaves us wanting -- many more, and better, elements of a comprehensive solution.


Dr. David L. Katz;

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