Can Obesity Be Growing if BMI Isn’t?

BMI is a just a number, but it’s one that people love to hate. A new research letter in the Journal of the American Medical Association (JAMA) gives more ammunition to BMI critics.

Earl Ford and colleagues from CDC analyzed data from the National Health and Nutrition Examination Survey (NHANES) to find that waist circumference grew significantly between 2000 and 2012. They found significant increases across the board: in men, women, non-Hispanic whites, non-Hispanic blacks, and Mexican Americans.

It was BMI data from this same source (NHANES) over the same time period that was recently used to proclaim that we’re “turning the corner on obesity” with prevalence of obesity stabilizing.

Ford prescribes caution about overemphasizing BMI, saying:

At a time when the prevalence of obesity may have reached a plateau, the waistlines of U.S. adults continue to expand. Our results support the routine measurement of waist circumference in clinical care consistent with current recommendations as a key step in initiating the prevention, control, and management of obesity among patients.

Using BMI as the sole criteria for diagnosing obesity will always be problematic. People who are intolerant of size diversity like it, though. Anyone over the magic number of 30 can be regarded with disdain. An equal and opposite reaction comes from people who use “BMI=30=obesity” in their straw-man argument that obesity is a bogus diagnosis.

The fact remains that BMI is a screening tool — nothing more and nothing less. So is waist circumference. Diagnosis of obesity requires a caring, skilled clinician.

Click here to read the analysis in JAMA and here to read more from Reuters. You can find more about waist circumference and BMI here.

30, photograph © Andreas Levers / flickr

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