Hey BMI – I Wish You Weren’t a Liar!
“Hey BMI – I Wish You Weren’t a Liar!” was actually an idea that popped in my head watching Anchorman: The Legend of Ron Burgundy. (It’s an okay movie; but if Oscar pieces are more of your interest, then you might want to pass on this one). When I saw the scene where Ron tells his co-worker that he wishes she wasn’t a liar, I immediately jumped off the couch and jotted down this blog post. I would like to relate it to an apple slamming Isaac Newton in the head, but I think that’s pushing it a bit.
The BMI measurement refers to the Body Mass Index, where your weight (in kilograms) is simply divided by your height (in meters squared). This standard is used to clinically classify obesity; a “healthy” BMI should range between 18.5 to 24.9 kg/m2 (1). So if you’re below 18.5 you need to gain weight, and if you’re above 24.9 then you need to get moving and lose some weight.
But not so fast – after all, you are more than just a number. Weight and BMI go hand in hand but the issue here is that the number doesn’t tell us much more about you and your body composition. What’s “body composition,” you say? Body composition is the breakdown of your body: how much muscle mass you have in relation to fat mass. It’s the best way to track your progress in a fitness program because you’re concern is to lose body fat, not just weight. A sport scientist will use a caliper to measure your skinfolds – which is the technique used to pinch the skin in several areas of your body. It’s a very scientific method to use because not only can a health professional track your fat loss, but s/he can also determine hormonal issues based on the skinfold measurements(2). So someone may have a healthy BMI but also a whole host of problems with testosterone, cortisol, and insulin. It’s not about a number, but what the number means that is important.
Unfortunately, the BMI doesn’t tell us this information. Furthermore, it’s flawed because many people are classified as overweight or obese because of the nature of their training. Those who regularly strength train are going to develop muscle, and muscle is going to give us a lean, athletic physique – but it will also make our BMI increase slightly.
Let’s use an example. Let’s pretend the webmaster here at UEFP is five feet, four inches and has a BMI of 26. This 26 classifies our webmaster as overweight. However, her body fat percentage is 11.8% (ideal for a female) and if you saw her, you probably wouldn’t consider her overweight. So she can rack her brain and try to get that BMI down (and lose a bunch of muscle in the process), or she can continue to get in shape and enjoy her life.
In cases for people who are morbidly obese, the BMI works just fine as a measurement for them to track. However, for most of us, that one number doesn’t really do us justice. Keep in mind that if you really want to get in shape, you have to get beyond what the scale says.
1. Colberg, Sherri R. “Nutritional Status and Chronic Diseases.” ACSM’s Resource Manual for Guidelines for Exercise Testing and Prescription. 6th ed. Baltimore; Lippincott, Williams, and Wilkins. 2010; pp 115
2. Berardi, John. Andrews, Ryan. The Essentials of Sport and Exercise Nutrition 2nd ed. Precision Nutrition. 2013.pp 317