Functions and Limitations of the BMI Calculator

BMI, which stands for "body-mass index", is a very popular measure for obesity. It is calculated by taking your weight in kilos and dividing it by the square of your height in metres. It is also known as the Quetelet Index, after its Belgian founder. It is used around the world by many governments in their official health standards. Find out a little bit more about the BMI and some objections against using this popular standard.What is Seen to be the Ideal Score?When you have a score of 20 to 25 you are seen to be of normal weight. Anything over 25 is overweight and over 30 is obese. Under 20 is considered to be unhealthy as well, because you are deemed to be scrawny--that is, unhealthy light-weight. You probably lack energy and are in need of muscle.Shortcomings of the BMI calculatorIf you are a runner who is going to use the BMI calculator to determine whether or not you are fit, healthy, or having success with your running or fitness program, you need to be aware of some shortcomings of the BMI calculation. First of all, Quetelet lived in the 1800s. People looked and lived differently back then. People were generally a lot shorter. The BMI calculator assumes an average lifestyle to begin with. This means it assumes that you are, for the most part, sedentary, with almost all of your physical exercise coming from walking, working etc. It also assumes that you eat a typical modern diet, which as we know by now is not all that good for keeping off the unwanted pounds. BMI Calculator: Problem with RunnersIf you are a runner, you are not the average person. You don't have a sedentary lifestyle and you will typically have made some conscious dietary choices as well. You will also drink more water than the average person today, and water consumption is well known for aiding weight loss. Now, this means that the BMI calculator could be problematic for you as a runner. It may show that you are "scrawny" when in fact it's obvious that you are all slender muscles and filled with vitality and energy.There are other potential problems that you may face if you use the BMI calculator as an indicator of health and wellness.BMI calculator: Problem with Older PeopleOlder people (people over 60) tend to lose an inch or two off of their height as they age, but they don't lose weight as readily as they did when they were younger. Therefore, if you're an older runner, the BMI calculator may show that you are "out of shape", probably "overweight" when in fact you are not.BMI calculator: Problem with an "ectomorph" body typeSome people are naturally just not as apt to put on weight as other people, yet they are not unhealthy at all. Asian people tend to fall into this category more often than other races. So if you are Asian, or if you know that you are an "ectomorph" body type, the BMI calculator may say you are in the 20 to 25 range while you are truly overweight (you have too much fat tissue, not enough lean muscle). Likewise, it may tell you that you are "scrawny" when in fact, pound for pound, you are quite strong.BMI calculator: Problem with Tall PeopleTall people (basically those over 6 ft. tall) don't do well with the BMI calculator. The calculation just doesn't consider them realistically enough, because back in the days of Quetelet, he did not have those people around to test his calculation!BMI calculator: Problem with Muscular PeoplePeople who are quite muscular don't do well with the BMI calculator, because muscle weighs more than fat. So, athletically muscular people very often turn out "overweight". Many of the elite 100-metre sprinters today are, based on BMI, overweight. Only Usain "Lightning" Bolt probably has a healthy BMI. He baffles scientists exactly because of that. He is considered to be not muscular enough for the speed he runs at!It is interesting to see that such a widely-adopted measure has got so many shortcomings for so many people. The body-mass index is simply out of date. Many governments however have not moved with the times yet and use this as a main measure for the health of their population. It is good to see that the New Zealand government has recently made some changes. It now uses a measure of the hip size and waist size as it has been proven that the ratio between those is very indicative of heart and cardiovascular problems later in life. And this makes sense: if you carry too much belly fat for your posture you are in trouble. Based on BMI all may still be fine if you are quite tall, but this new ratio explains better whether you are healthy or not. Going forward we will see officlal institutions and governments move away from using BMI and move to using other measures. Measuring your health or success as a runner can thus better be done by pure weight loss, by changes in your clothing sizes, your belly fat, the time spent running etc. rather than by BMI. You can still use it as a gauge, but by no means feel controlled by it as there are many, many people for whome this calculation is past its' due date!