BMI Is Inaccurate, So Try the Body Shape Index Instead

You've probably heard of the Body Mass Index (BMI) — it's a simple way of combining data about height and weight to give a rough estimate of whether your weight is healthy or not. But the BMI has several limitations, and is only a crude indicator of health. It is better used to judge weight trends in a population rather than in any one particular individual. So, researchers at City College in New York City have developed an alternative to the BMI called A Body Shape Index (ABSI), which takes waist circumference into account.

With waist circumference info, the ABSI can give a more accurate idea of weight-related health risks to people who may be dense and muscular (like athletes) but with healthy-sized waists, and to people who may be kind of "skinny fat," with a dangerous amount of fat around their abdomens. Abdominal fat is bad news, because it's related to heart disease and metabolic disorders like diabetes.

I was reflexively skeptical about the ABSI, as I am about all health headlines, but decided to check it out. The DailyMail makes it sound like ABSI is very difficult to measure (requires "computer software!") but there are simple calculators readily available on the Internet, including this one. A score of 1 means that your risk of dying is average, even after controlling for other health and demographic characteristics.

As for me: I am 5'5" and 162 lbs., which tends to surprise people, because that's pretty damn heavy, but I comfortably wear a medium size in all garments. For reference, the last jeans I bought were a size 10 at Express (I was feeling a little high school nostalgic, don't judge). Here is a pic of me wearing an impulsively-purchased Forever 21 crop top:

No washboard abs, but pretty unremarkable, right? Well, BMI-wise, I am a 27: firmly in the "overweight" category. This has always frustrated me, because even when I exercise more, I don't really lose weight. In fact, it took eating fully vegan for me to drop down to the "normal" category, but I was hungry, blood sugar crashy, and scrawny-looking.

Compare that to my ABSI: with a respectable 29-inch waist, my 5'5", 162 lbs. frame earns a ABSI score of .68. In other words, my score is significantly better than average, and indicates that women my size bear a much lower than average risk of mortality compared to other American women our age. Not bad, I'll take it.

So, my experience is one data point confirming that "ABSI had little correlation with height, weight, or BMI." Though my ABSI is low, I'm not short or light, and my BMI kind of sucks. I'm not trying to rationalize my weight or size — I'd lose weight if I thought it'd save my life — but ABSI really does seem to be a better indicator of mortality risk than BMI. Knowledge is power, so try a calculator (this version shows both measures side-by-side) and see if BMI has been lying to you all along.