Measuring Body Mass Index (BMI): A Reliable Diagnostic Tool?
One of the most interesting, as well as puzzling things to me as an Austin personal trainer for over 20 years, is to hear people extol upon the virtues of formulas. In the world of health and fitness, there are many sweeping statements and generalizations concerning everything from our performance levels should be, how many calories we should ingest, to things such as what our maximum heart rate is. It takes just a little bit of common sense to realize that these are fallacies. The BMI chart is no exception.
If we look at the formula used by most personal trainers, and many physicians, for that matter, to determine one’s maximum heart rate, it is obviously flawed, and furthermore, to base one’s exercise regimen upon it, would be downright dangerous. The practice of subtracting your age from the number 220 to determine your maximum heart rate has no merit because there is nothing personal about it. It’s a random number with genetics and predispositions tossed to the side. Imagine, 10 people in a room who are all the same age. Is it rational to assume they all have the same maximum heart rate, and should exercise as such?
Heart rates and caloric indulgences and deficits are not alone in the world of health and fitness falsehoods, misgivings, and generalizations. One of the biggest, and most widely misunderstood generalizations out there is the Body Mass Index, or BMI, for short. So, what exactly is the BMI?
The body mass index, or BMI chart, is simply a chart which has on one side weight in kilograms which is to be divided into the square of the height, which is measured in meters. It’s sole purpose, is to determine if a person is obese, or not, by plugging in the above numbers and running the calculation.
Oddly enough, by the Center for Disease Control’s own admission, and on their website, there is only a slight correlation to one’s BMI and their actual levels of body fat, and that furthermore, BMI is not a reliable diagnostic tool in determining fatness or health. Strangely, it’s seen as a common medium and measurement by healthcare professionals as well as many personal trainers. The fact that it’s an arbitrarily concocted number, without the benefit of relativity, has yet to persuade many institutions and gyms from curtailing it’s relevance.
If, for example, we took a person who was 6 feet tall and weighed 220 pounds, and had a correspondingly low body fat measurement of perhaps 12%, would it be safe to assume that because their weight is much less fat than muscle mass, that they are a strong and likely healthy athletic type? One would think, but you would be mistaken. Despite the fact that a 12% body fat measurement is usually typical for an athlete, as opposed to the layman, the BMI chart has this person categorized as overweight, and bordering on obese, with a BMI score of 29.8 with a score of 30 the threshold for clinical obesity. According to the chart, the normal weight for an adult male who is 6 feet tall is 136 to 184 pounds.
I can only scratch my head and wonder how this is an acceptable norm when everything, such as body fat measurements, genetic makeups, as well as age and levels of athleticism are categorically dismissed. To further reference the above example, to call an adult male with a 12% body fat measurement obese, is a far cry from reality, and science.
Any calculation in the health and fitness world, and even in the medical community, from needed calories, to BMI, and on to where one’s maximum heart rate lies, has to be considered on an individual basis for it to be a valid calculation and worthy of consideration. To make random statements without the benefit of the counterbalance of relativity, is not only worthless, but it’s irresponsible, and potentially dangerous.
If you are considering working with a personal trainer, for whatever your goals may be, be sure to ascertain that the trainer has a competent and thorough working knowledge of what BMI truly means, or in most cases, doesn’t mean. If you are simply weighed and then your numbers are thrown into a preconceived formulaic calculation, the results will be impersonal, at best. The same can be said for the measurement of your maximum heart rate. Don’t pull out the calculator and abide by an antiquated formula which can’t possibly differentiate between you and another person of your same age, but rather seek a personal trainer who understands wherein the difference lies between formulaic training and personal training.
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Andy
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