Do you know your body weight measurement (BMI)?

Most likely you do. For two decades, the rather simple BMI equation (your weight in kilograms divided by the square of your height in meters) has been the medical community’s preferred way of determining who is “underweight,” “normal weight,” “overweight” and “obese.”

Yet, as an article published earlier this week in the online magazine Slate points out, the researcher who developed this formula in the early 1970s — University of Minnesota physiology professor and obesity researcher Ancel Keys — never intended it to be used for this purpose. He envisioned BMI only as a useful tool to help epidemiologists estimate and compare overall obesity levels of large populations from huge pools of historical height and weight data.

“His original paper warned against using the body mass index for individual diagnoses, since the equation ignores variables like a patient’s gender or age, which affect how BMI relates to health,” writes Slate reporter Jeremy Singer-Vine. “It’s one thing to estimate the average percent body fat for large groups with diverse builds, Keys argued, but quite another to slap a number and label on someone without regard for these factors.”

Yet slapped on us it’s been, as Singer-Vine points out:

During the past decade or so, a growing number of studies and journal reviews have begun to caution against relying too heavily on BMI as an indicator of a person's risk of disease. Even its use in research, notes Singer-Vine, is being challenged:

As BMI's critics have pointed out, there’s a better alternative for figuring out if you’re at a healthful weight. Writes Singer-Vine:

In fact, a European study recently found an association between having a large waistline and a doubling of the risk of dying prematurely from heart disease, cancer and other chronic medical conditions. And, as I reported last year, other research has found a link between abdominal obesity and an increased risk of Alzheimer’s disease.

So get out the tape measure. Abdominal obesity is currently defined in men as having a waist circumference greater than 40 inches and in women as having a waist circumference greater than 35 inches. Some experts, however, believe those numbers are too high. Stay tuned.