Monday, July 29, 2013

Why I Hate the BMI Scale

It's no secret that I am NOT a fan of the BMI scale.

Before I go into why I dislike the BMI scale, a little information.  For those of you who are not familiar with the BMI scale, here is a basic chart to get you started:



Or, if you're a hands on type, you can manually calculate your BMI as follows:

         ( Your Weight (LBS) / Your Height Squared (IN) ) x 703


So, for example, if you are 5'8" (68") and weigh 180 lbs, you would calculate as follows:

         ( 180 / (68 x 68) ) x 703 = 27.37 BMI


The theory behind BMI is that by simply weighing a person's body mass and measuring their height, one can calculate a person's general body composition and determine their "overall health".  I use the term "overall health" loosely.  But, generally, BMI is used as an indicator of body fat percentage and the medical industry uses it to classify patients into various health risk categories.

If you research more on BMI, you will find that the formula (previously called the Quetelet Index for BMI) dates to the 19th century.  The shortened term "body mass index" or BMI, dates to a paper published in 1972.  Wow, modern science at play here. Anyone see a red flag yet?

Here's where it gets even better.  In the 1972 paper on BMI, it was explicitly cited that BMI is appropriate for population studies, and inappropriate for individual diagnosis. Hmmm...

So, why is my doctor using the BMI to assess me, you ask? 

Well, due to its simplicity, BMI came to be widely used for individual diagnosis, despite its inappropriateness.  BMI provides a simple numeric measure of a person's thickness or thinness, allowing health professionals to discuss overweight and underweight problems more objectively with their patients. However, BMI has become controversial because many people, including physicians, have come to rely on its apparent numerical authority for medical diagnosis, although that was never the BMI's purpose.  Truly, BMI is meant to be used as a simple means of classifying sedentary (physically inactive) individuals, or rather, populations, with an average body composition. 

SUPER DUPER!  The medical industry is using a tool meant for general data collection to classify me as an individual!  (*insert eye roll*)

The thing that is most maddening to me about this is the CDC website itself.  Check it out.

I could list a ton of direct quotes from that website, but I'm going to focus on this one:

"BMI is used as a screening tool to identify possible weight problems for adults. However, BMI is not a diagnostic tool. For example, a person may have a high BMI. However, to determine if excess weight is a health risk, a healthcare provider would need to perform further assessments. These assessments might include skinfold thickness measurements, evaluations of diet, physical activity, family history, and other appropriate health screenings."

Have you figured out why I'm hating BMI yet?  LOL! 

Just remember this blurb from above, it will be important soon:  "A healthcare provider would need to perform further assessments. These assessments might include skinfold thickness measurements, evaluations of diet, physical activity, family history, and other appropriate health screenings."

Before I get too far, by now, I'm hoping you've read this post.  If you haven't, swing by there and take a look.  Because sh!ts about to get real.

In 2011, after dropping my weight down from 240ish to about 190, I decided to finally buck up and go back to the doctor.  I'm ashamed to admit that I was so upset with my body weight that I stopped going for my yearly visits... and for longer than I'm willing to document here.  Yes, I deserve a swift kick to the nuts for that.  No, I am not proud of it.  But I think it says something about a doctor's bedside manners when you're so ashamed of your weight that you can't fathom going back for another visit.

Anyhow, in 2011, happy with my weight loss progress and knowing I was more than overdue, I decided to ditch my unfriendly doctor and try out a new place.  Since a new medical center just opened not far from my house, I decided to try my luck and had my medical history transferred there.

While we wait for the doctor, let's queue the standard waiting room elevator music...

And here comes the awkward height and weight measurement by the first available nurse.

Of course, at this point I'm stuffed into an exam room to wait for a doctor to come.  When she finally gets into the room, I get my standard pokes and prods. 

Now comes the fun part, the weight discussion.  I'm paraphrasing, but the conversation goes something like this:

Dr. - Well, Natalie, let's talk about your weight.

Me - Ok... (starts to nervously sweat, not kidding - I left with sweat stains).

Dr. - You could really stand to lose a few pounds.

Me - Well, actually I wanted to talk to you about that.  Because about two years ago I maxed out at 240 and...

Dr's eyes pop out of head.

Me - And so I'm wanting to know what's realistic here.  You see, I'm the most fit now that I've ever been in my life.  I've got more muscle in my arms and thighs than I know what to do with.  I go to the gym, yoga or run at least 5 times a week, if not more.  At what point do you take into consideration my muscle weight versus my body fat percentage?

Dr. - You lost this weight by yourself?

Me - Yes.  I've been doing it slowly for the last couple of years.  Mostly I try to make sure I'm eating a balanced diet, and like I said, I work out a lot.

Dr. - Well, that's good.  It's important to lose weight slowly.

Me - Yes, I understand that.  (Hiding eye roll).  So what about my ideal weight?  Because I don't think it's realistic for me to try to hit BMI's suggested 160 based on how muscular I am now.

Dr. - Do you know your current BMI?

Me - Yes.  I know even with where I am at now, I'm borderline overweight to obese.  Which doesn't make any sense to me given how active I am.

Dr. - (Noticeably surprised that I am aware of this) Well, let's bring up a BMI calculator. 

(I'm not even kidding, this doctor who is medically trained, had to bring up a calculator tool on her computer to type in my height and weight in order to see my results.  She didn't even have a chart handy or anything.)

Dr - Yes, you are right.  You are just on the edge of overweight to obese.  Your ideal weight should be in the range of 130ish to 165ish.  Keep up the good work, you'll get there.

Me - But that's not my point.  I know I am way more active than any person you could bring into this office that also weighs 190.  In fact, I'm wearing a size 12 pants right now.  The last time I wore a size 12 pant, I was in college, weighed 165, and hardly worked out.  I weigh 25 pounds more NOW at the same waist size THEN.  That tells me my muscle is really weighing me down.  How do I factor in my muscle mass to determine my true BMI?

Dr - Well, the BMI tool is pretty accurate.  Unless you are an Olympic type muscle builder or something like that, you should really abide by it.

Me - That's fine.  It just doesn't seem reasonable to me to get down to 130-165.  I'd be 5'8" and wearing a size 4.  I'd be a skeleton.

Dr - Maybe you can set your goal for 170.  I think that would be OK.

AAAAAANNNNNDDDD, end scene. 

Notice the lack of caliper employment or questions about my physical activity (IE type/duration).  Even more frustrating, I straight up told her I am wearing a waist size at 190 that used to fit me when I weighed 165.  Obviously there is huge muscle mass at play.  Despite my questions and wanting a fat analysis of some sort, in less than 10 minutes the doctor has given me a standard physical and brushed me off as overweight despite the above conversation.

BMI is so maddening!  Even more so to be someone who weighs 240 and is trying to make a change.  Imagine wanting to lose weight and seeing that you qualify as borderline severely obese.  If that isn't enough to shut you down before you even try to start, I don't know what is.

At the end of the day, I don't know who to hate more... the BMI scale for existing, or the medical industry who has changed the BMI scale from "a tool meant to make generalizations" into "the gold standard for judging individuals".  BAH!

So, if I hate BMI so much, what DO I recommend?

Personally, I'm a fan of any diagnostic that takes multiple measurements into play.  Right now, I find this tool to be particularly interesting, since it tells you an estimated body fat percentage.  I'd far prefer to know much muscle I have versus fat, instead of how my overall body mass relates to my height (*gives BMI the evil eye*).

If you're curious, here's a fat percentage chart:



Fun fact - as of today, according to BMI, I am still overweight.  But, based on my height, weight, waist, hip and other measurements, my body fat percentage is solidly in the average category, not even close to bordering on obese.  Anyone see any possible problems there?

So, my parting words of wisdom are this.  BMI is a tool, not a golden rule.  If you are working out and maintaining a healthy diet, the rest will fall in line, even if it takes a little time:




Screw BMI!  :-)

2 comments:

  1. At the place I go to for medical services they use the terms "morbidly obese," and "super obese." Morbid is such a negative word. Recently my weight was recorded in error as morbidly obese. Actually I'm overweight, according to the BMI scale. When I saw morbidly obese I went ballistic. I hate the BMI scale as much as you do. I've become a body builder since loosing 50 pounds - by the scale. But I don't know how much fat I've actually lost or what my percent of body fat is. But there is a way to find this out accurately - with a full body dexa scan. Eastern Michigan University used to offer this at a very reasonable price. I'll be checking into this soon.

    Yeah, I knew the "morbidly obese" notation on my record was an error. But it still made me mad. I raised hell about it!

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