What Does Body Mass Index Mean

What does body mass index mean? This term is one that causes a lot of confusion in many people. You’ve no doubt heard the rumor that body mass index (BMI) can be inaccurate. This has caused many to disregard the method. Despite the BMI being inaccurate in some cases, for most people it’s a perfectly valid means of assessing healthy weight.

So what does body mass index mean?

The body mass index was created between 1830 – 1850 by Adolphe Quetelet. The body mass index calculates a persons mass (height to weight ratio) compared to the average height to weight ratio. The healthy range was determined over several decades based on medical records showing disease rate patterns associated with certain body mass index results. For example, people with below average BMI calculations may suffer from malnutrition, infertility, osteoporosis, anemia, weak immune system, bulimia and anorexia. Oddly enough, underweight people suffer similar mortality rates to those who are obese! People with a high BMI are more likely to suffer from high blood pressure, heart disease, diabetes, infertility, sleep apnea and stroke. The healthy weight range is applied to the range with the lowest percentage of these ailments.

So what is a healthy BMI?

There are several classifications

Severely Underweight	BMI Under 16
Underweight	BMI 16 – 18.4
Healthy Weight	BMI 18.5 – 25
Overweight	BMI 25.1 – 30
Obese	BMI 30.1 – 35
Severely Obese	BMI 35.1 – 40
Morbidly Obese	BMI over 40

Is it accurate?

Some people choose to disregard the body mass index because in certain cases it is inaccurate. But unless you have the fitness and strength of an athlete, your BMI should be accurate. Only those with a high percentage of muscle like athletes and those with physically demanding jobs (builders etc) will have an issue of accuracy with the BMI. This is because muscle weighs approximately 18% more than the same volume of fat. So if you have two people of an identical height and weight, one can be obese while the other could have virtually no fat simply because they have a higher percentage of muscle. In the case of athletic people, further tests are required to accurately assess body fat percentage.

Another thing that can cause issues is the fact that BMI over generalizes by not taking frame size into account. For example, small framed people may carry excess fat for their height despite having a “healthy” BMI. Large framed people may have a low body fat percentage but be classified as “overweight” according to their BMI. This is because BMI is based upon a range which tries to take too many variables into account. So you need to know your frame size also. Click here for information on how to calculate your frame size

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