Does BMI Really Reflect Health?

A while ago, writer Kate Harding put together a slideshow to illustrate how random BMI standards can be. The slideshow features photos of dozens of women with captions announcing their names and their BMI standards: "Kate is obese," "Mindy is normal," "Pippa is normal," etc.

The juxtaposition of the image and the loaded term -- "normal," "overweight," "morbidly obese" -- is shocking, and shows just how cold and distant these medical distinctions can be from women's lives and bodies. Many of the women characterized as "overweight" in particular seemed healthy to me, and shared body types similar to many active, happy healthy women I know. However, a trip to the doctor's might deem them otherwise.

The New York Times recently took up this issue in an article entitled "Weight Index Doesn't Tell The Whole Truth." The piece explains BMI standards: a BMI of less than 18.5 is "underweight," 18.5 to 24.9 is "normal" or "healthy," 25 to 29.9 is "overweight," 30 to 39.9 is "obese"; and anything over 40 is "morbidly obese." It then shows how these terms can be misleading: a lower BMI can indicate malnutrition, cancer, or anorexia, and a higher BMI doesn't necessarily mean that a person is overweight or has too much body fat.

BMI doesn't distinguish between fat and lean muscle tissue, an amazing oversight which implies that a person whose BMI indicates they're overweight or obese could actually have far more lean muscle tissue than fat, and a person flagged as normal or healthy could have mostly fatty tissue and little muscle. The New York Times quotes Dr. Carl Lavie, the author of a study that addresses the problem of BMI standards, as saying, “Although B.M.I. is the most common method to define overweightness and obesity in both epidemiological studies and major clinical trials, clearly this method does not necessarily reflect true body fatness, and B.M.I./body fatness may differ considerably among people of different age, race and sex.”

Seems a little problematic then, doesn't it? If the BMI doesn't actually reflect "true body fatness" or take into account any distinctions of age, race, and sex, than perhaps its at best an outmoded, ineffective, and ultimately demoralizing standard by which to judge a woman's health?

And, to push that idea a little further, might it not indicate some of the problems our medical culture, and our culture in general, deal with when trying to classify and explain women's bodies: that health cannot always be judged on image alone, and that developing a uniform standard for "healthy" vs. "fat" or "undesirable" bodies is inherently problematic? I fear that the death of BMI won't also indicate the slow decline of the need to develop a uniform system for measuring and judging bodies, but rather will simply mark the cry to initiate a new system, with new, equally rigid standards and categories.

Photo credit: Bob B. Brown