Muddled Thinking and Silly Arguments About BMI

It’s great sport or a great folly. Body mass index – BMI – is a simple measure and an easy target for so many people. It saves many people for many reasons from having to think about obesity. Clinicians who don’t want to think too hard about obesity might use BMI, mistakenly, all by itself, to define obesity. Others, who’ve been targets of such misuse of BMI, use those mistakes to refute the concept that obesity is a health problem. And in fact, this line of arguments has taken the form of a resolution for the AMA to “support removal of BMI as a standard measure in medicine.”

Don’t Look?

This resolution comes to the AMA House of Delegates from the Medical Student Section of the AMA. The annual meeting of the House of Delegates starts tomorrow. It was at the 2013 meeting of this body that the AMA decided obesity really is a complex, chronic disease – albeit not one defined solely by BMI.

Resolution 435 has a lot packed into it. It strings together 22 instances of “whereas,” making it clear that the authors have a whole lot of reasons for hating BMI. Right up front, it makes the point that assuming BMI is a measure for adiposity constitutes a fatal flaw. The resolution covers problems with using the same benchmarks of BMI in different racial and ethnic groups. Then it also explores issues of stigma attached to obesity, as well as eating disorders. It covers a lot of ground.

But the bottom line is to suggest that BMI only be used “in a limited screening capacity.”

Don’t Get Carried Away

We’re not sure how to reconcile the topline of this resolution with its bottom line. Right up front, the title says the resolution is for “removal of BMI as a standard measure in medicine.” But the bottom line is not so bold. It calls to use it in a limited way – only for screening.

Of course, this latter line of thinking makes sense. BMI is useful because it’s simple, though it has very real limitations. It’s worth looking at. But it doesn’t tell the whole story of health and obesity. For that, a good clinician will consider the whole person and their health – past, present, and future.

Arguments about removing BMI as a clinical measure might draw attention. But they distract from a deeper understanding of obesity and health. These arguments are persistent and tiresome.

Click here for the text of Resolution 445 submitted to the AMA House of Delegates and here for more perspective on issues people have with BMI.

The Blinding of Sampson, painting by Rembrandt / WikiArt

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June 9, 2022