BMI sucks. Use the Beast Index™

Roughly speaking, the Body Mass Index (BMI) is a relative measure of body mass to height.  Originally developed in the mid-19th century, BMI is an attempt to quantify an individual’s tissue mass and then categorize that person as underweight, normal weight, overweight, or obese based on that value.


There is plenty of criticism of BMI as a measure of health. Because this is my blog, I’ll focus on the issue most relevant to me: the total lack of distinction between fat and muscle. As obsesity researcher Peter Janiszewski put it,

BMI does not differentiate between the Michelin Man and The Terminator.

I’m decidedly not the Michelin Man, but BMI says that I’m overweight. Before you call me vain, there are potential ramifications here—insurance companies use BMI as a measure of health when setting premiums. Oh, and I am vain. And I don’t like being told I’m overweight. Just kidding, I don’t care. Well, maybe a little. But I digress.

Despite the criticisms, BMI is apparently useful at a population level for assessing health, the idea being that the average person falls somewhere in the middle of the Bibendum-Schwarzenegger spectrum.  And it is pretty easy to calculate, which makes it relatively useful to those who don’t have body fat analyzers, skin calipers, or the neuroses to even consider buying such things. But for those of us who do, I propose a new measure: the Beast Index™

The Beast Index™ is a measure of BMI relative to body fat percentage.  Whereas BMI only measures mass relative to height, and whereas body fat only determines whether one is skinny, the Beast Index™ combines both for an approximate measure of swole-ness.  Put simply, the higher your Beast Index™, the more likely you are to be mistaken for a superhero.Beast Index Chart

Scientists are still determining the optimal Beast Index™, but suffice it to say that a measurement around 3.5 is solid—you’re sufficiently swole as to avoid being mistaken for a cancer patient without looking like some sort of science experiment gone awry.  As the chart above shows, the 1-2.5 range is the fat part of the bell curve. If you lose some fat, you can move to the right tail…and probably get more tail.

It’s worth noting that the Beast Index™ corresponds roughly with the venerated Mazzetti scale as follows:

  • 5+: Freak Beast
  • 4.5-5.0: Monster
  • 3.5-4.5: Gym Rat
  • 2.5-3.5: Gym Bro
  • 1.5-2.5: Brotege
  • 1-1.5: Tadpole
  • <1: Primordial ooze

One thought on “BMI sucks. Use the Beast Index™

  1. BMI is a joke. I was a serious weightlifter for 24 years, I ran a landscaping company single-handedly and climbed mountains on the weekend. My blood pressure was perfect, my cholesterol was perfect, every possible way to take an obscure measurement of my health was perfect. Then they put me on a scale.

    They told me I was obese. I was tighter than a board, was pressing 625 lbs on the sled at a hard core gym, could out-hike any physician in the building and arm wrestle them under the table but because I weighed more than what a 5’7″ women should weigh on their little health insurance chart, I was given a black mark. They even tried to schedule an appointment with a dietitian!

    I told them, “I’m not talking to anybody else who has biceps smaller than mine,” and I never went back. Now I only seek emergent care if I’m bleeding. I don’t need a chart to tell me when to get stitches.


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