Thursday, June 25, 2015 6:39 PM

What is my BMI and should I care?

So you have been using the CMC Employee Fitness Center regularly right?  (pssssst...This is where you nod and tell me yes!) Hopefully you are starting to see some changes by now.  You might be doing some research on your own, trying to figure out how to maximize your gym time and set some goals to shoot for to keep motivated.  A lot of us are motivated by something easy to quantify or measure.  NUMBERS!  

That’s easy to measure and track!  Everyone loves seeing numbers change, i.e., body fat % g oes down, HR goes down, BP and cholesterol go down, weight lifted goes up, mileage goes up, treadmill speed goes up, BMI goes down…

Whoa!  Hold the phone!  BMI?!?!?  What is that and why do I care?  BMI or Body Mass Index is basically a ratio of body mass to height created by Belgian Adolphe Quetelet between 1830-1850 as he was developing something called ‘social physics’, whatever that is.  Anyway, I digress.  BMI really didn’t hit its stride until the 70’s when it began to be popularly accepted as a standard way to classify body fat percentage in relation to height and weight.  Even to this day it is viewed as being appropriate for ‘population’ studies.  Key phrase there: ‘population’ studies!  The problem is due to it being simple and easy to use it is used all too often for individual cases as a means of classifying sedentary individuals.  So you see BMI is a VERY broad or G-E-N-E-R-A-L guideline.

Who really cares about BMI you may be asking yourself right about now?  Insurance companies do when they are writing your health insurance policy.  It definitely affects their bottom line.  Of course it is all about money!  BMI is very commonly used as a guideline for medical underwriting in private health insurance plans.  Most private health insurance providers will use a high BMI number to indicate someone who is likely to be a higher risk patient and set a higher insurance rate at this point.  This will also allow the provider to offer a reduced rate to those in the lower BMI range.  This cutoff point is determined differently from provider to provider as well as different ranges of acceptability.  



So now I am sure you are sitting there asking yourself is this a good or bad thing?  Well that depends but remember this BMI range is a loose and G-E-N-E-R-A-L guideline.  A pretty commonly accepted number of 25-30 indicates an ‘over weight’ category.  Now let’s take my own personal dimensions into account as an example.  I stand 6’0” tall or 72” tall.  I just stepped off the scale here in the CMC Employee Fitness Center at 193.6lbs, maybe fully clothed we can subtract 5ish lbs.  However, for easy math sake and because I only have ten fingers and ten toes to do math with lets round that weight to 190lbs.  So here is what the equation and calculation will look like using my numbers;

[weight ÷ (height)2 ] 703= BMI  
(703 being a conversion factor)
[190 ÷ (72)2 ] 703 = BMI
[190 ÷ 5,184] 703 = BMI
[.036651] 703 = BMI
25.76 = BMI


If you recall we established the fact that a BMI in the 25-30 range was considered ‘over weight’.  Just to confirm my math was correct I used an online BMI calculator and came up with 25.8 as well.  If you have seen or met me personally I think you would find it hard to believe that I would qualify as ‘over weight’.  You have to remember BMI is using your total body weight or what is on the scale.  BMI is NOT a measure of how much fat someone is carrying around and is calculated from an individual's weight which includes both muscle and fat.  Due to this some people may have a high BMI but NOT a high percentage of body fat. 
 

So long story short or in this case, long story longer; DON’T worry about BMI!  It is too general and broad to concern yourself with.  Not just that but controversial as well!  Check out what some of the experts have to say about it;

 
"Mathematician Keith Devlin and the restaurant industry association Center for Consumer Freedom argue that the error in the BMI is significant and so pervasive that it is not generally useful in evaluation of health.

University of Chicago political science professor Eric Oliver says BMI is a convenient but inaccurate measure of weight, forced onto the populace, and should be revised.

A study published by Journal of the American Medical Association (JAMA) in 2005 showed that overweight people had a similar relative risk of mortality to normal weight people as defined by BMI

Dr. Carl Lavie, a cardiologist at the John Ochsner Heart and Vascular Institute, as quoted in the New York Times, “Although B.M.I. is the most common method to define overweightness and obesity in both epidemiological studies and major clinical trials, clearly this method does not necessarily reflect true body fatness, and B.M.I./body fatness may differ considerably among people of different age, race and sex.”

Dr. Steven Novella, a Yale physician, has examined the BMI “controversy” in-depth and states, “It is widely recognized and admitted that BMI is problematic as applied to individuals. Muscular and athletic people may have a high BMI and not have excess adiposity, for example. Also at the extremes of height the BMI becomes harder to interpret.”

It might also be worth pointing out that Adolphe Quetelet the creator of the BMI was a mathematician/statistician and NOT a physician.  Just sayin’.  What are your thoughts on BMI?