BMI as a Weight Standard


The Military times has an article, “And the Fattest US Military Service is…”

Don’t bother to look for the Coast Guard in the listing, because we have been ignored again, but what I really wanted to address, is the use of BMI (Body Mass Index) as a standard. The standard of “fattest” was based entirely on exceeding a BMI of 25.

During my last tour, there was a petty officer I talked to frequently, who the Coast Guard was going to discharge because he was “over-weight.” In fact he was a rather large body builder, with very little fat on his frame. This was the kind of guy you want on your boarding party because he could be physically intemidating. We were going to discharge him, not because he was not in good shape, but because he was too muscular.

Body Mass Index was devised in the 1830s by Lambert Adolphe Jacques Quetelet. Let’s take a look at the formula for BMI:

weight (in kilograms)/height (in meters) squared

Note that it is height squared, but people are three-dimensional. If you really want to look at a proportional measurement you should use height cubed.

Looking at “25,” the upper edge of the nomnal normal range of BMI, the associated weight for different heights looks like this:

  • 6’4″– 205
  • 5’8″– 165
  • 5′– 128

If on the other hand, if we assume the BMI chart is right for 5’8″ but made the other two weights proportional to the cube of heights, the upper limits would look like this.

  • 6’4″– 230
  • 5’8″– 165
  • 5′– 113

BMI favors short people, while the tall are penalized.

At best, BMI should be used as a screening measure, but even in this role there are better formula available.

Before we destroy a service member’s career, we ought to be willing to base the decision on actual body fat content or a performance standard relivant to job performance.

4 thoughts on “BMI as a Weight Standard

  1. The BMI is way outdated and should be replaced with a meaningful measurement, if one is actually necessary.. I personally have never met the 25 BMI standard and have stayed in the 26 to 27 range my entire life. I lift weights and have been involved in martial arts most of my life.

    The military has set standards of fitness for its members, so why is the BMI so important for a measure of health and fitness? Seems physical fitness is more accurately demonstrated through performance and endurance, not by some ancient chart. The inaccuracy of the BMI scale misrepresentations can simply be seen through different individuals and their mass structure.

    Body fat can only be measured by hydro scaling. That is the only accurate and scientific method.

    Aside from that, everyone’s body and metabolism is different. Some individuals require a greater store of fat than others as their bodies use energy a little more efficiently. Too little body fat in adverse or severe situations and the system will start burning muscle tissue, and to some degree it does that anyway.

    You will never see a champion martial artist, some one involved in MMA, wrestling, or boxing, with a 25 BMI. NEVER!!! A person with a 25 BMI will never have the strength, stamina and endurance to be successful in meaningful competition.

    This arbitrary BMI standard equates to get rid of everyone over thirty five years old because they have passed their best physical years. And it is that: just a arbitrary standard!

    Seems the Pentagon’s regulations are still left over from the Civil War. Seems what may really need measuring is levels of intelligence at the Pentagon.

  2. I am sure BMI is reasonably accurate for men near the average height of men in 1830 which would probably be under 5’8″, As we move away from that average height, it becomes more problematic. I doubt if the original research even considered women.

    The term overweight carries a negative connotation, when some extra weight might be a good thing, if it were extra muscle. Higher than normal is a more neutral term.

  3. If we are going to set arbitrary standards for servicemembers’ shapes (since we test fitness separately), I propose that the military simply regulate the sizing of uniforms. If you can’t fit the uniform (mostly pants’ waistline), you’re too chubby. It’d be just as unscientific, but at least it would directly reflect professional appearance standards.

  4. Pingback: Possible Checks/Alternatives to BMI as Weight Standard | Chuck Hill's CG Blog

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