Let’s suppose the Seahawks are scheduled to meet the Patriots in Super Bowl 49 on February 1st, 2015 in Phoenix, AZ. The crowd is streaming into the stadium. The camera crews are in place. The beer commercials are all shot and edited. The half time show starring Katy Perry is prepared to do three of her most recent hits in the midst of smoke and lasers.
Russell Wilson leads the Hawks out of their locker room, and Tom Brady leads the Pats out of theirs, when suddenly they both notice that the field has yet to be lined out with chalk. There are no yard lines and no hash marks. They can barely make out the sidelines or the respective end zones. There’s also no chain crew to show where the ball is supposed to be placed, and how many yards the team must go in order to make a first down.
Brady looks at the ref and says, “How are we going to play a football game on a field with no yard lines? Wilson chimes in with, “How am I going to know what plays to call next, or whether we’ve scored a touchdown when we can hardly make out the end zone?
Let’s Stop and Confess…
OK, let’s stop the story right here and confess that we all know this could never happen in the midst of an NFL football game, let alone the Super Bowl. God forbid!! That would confuse the brats and burgers out of everyone and render the entire game meaningless. You could have no Super Bowl Champ, no meaningful winners or losers under such conditions, right?
But ironically, that’s precisely what’s been happening for the past two decades in the field of childhood obesity. The experts* have been researching and spending all kinds of time and boatloads of money in an effort to determine whether anyone is gaining or losing ground. And they’ve based those determinations on a measurement tool (BMI) that tells them almost nothing about changes in the body fat levels among children.
In other words, using BMI as their measurement tool of choice to document obesity (levels of body fat) changes in children renders their efforts as meaningless as a football game with no yard markers. And the results of this self-inflicted inability have been devastating to millions of kids around the world.
More specifically, since the formula is body weight divided by height squared times 703, (notice it asks nothing about body fat) BMI is completely and totally unable to distinguish 10 lbs. of body fat from 10 lbs. of muscle mass. That is to say, although it sounds official and scientific, BMI tells you no more than the common bathroom scale when it comes to the one and only thing that counts, changes in the percentages of body fat of the kids that are being measured!
Invalid for the Individual But Valid for the Many???
The conventional bureaucratic response to this challenge is to confess that BMI is invalid when it comes to measuring body fat changes of an individual. Then they turn right around and contend that when it comes to measuring mass populations (like a bunch of kids in a school system) BMI is suddenly valid. When asked why BMI is invalid for one individual yet valid for a thousand or ten thousand individuals, THEIR SILENCE IS DEAFENING!!
In reality BMI does little more than confuse the conversation (the emperor’s new clothes are beautiful aren’t they?) and undermine any legitimate possibility of measuring changes accurately. And this counterproductive state of confusion is destined continue until BMI is replaced with an alternative that’s both accurate and affordable.**
When that happens, the phrases research oriented and data driven will finally have some meaning in the field of childhood obesity. But until then they don’t, and we’ll continue spinning our wheels and losing the war against America’s number one health threat. Way to go team!!
*The US Center for Disease Control has been the lead proponent on behalf of BMI for well over a decade now. But following immediately in their wake (among many others) is the American Medical Association, the American Academy of Pediatrics, the American College of Sports Medicine, and the Cooper Clinic who, in conjunction with the NFL, authors and publishes the Fitness Gram which is used by most American schools to measure student fitness and body fat levels.
**BMI is the CDC’s measurement tool of choice because the conventional alternatives (skin fold, electronic impedance, and hydrostatic weighing) are too labor intensive and thus too expensive to use in mass testing. In other words, BMI wins by default because it’s CHEAP on the front end. But since it actively impedes any documentable progress, BMI has proven to be incredibly EXPENSIVE on the back end and thus is in dire need of being replaced ASAP!