<Handal> D-26: Your BMI Is NOT an Indication of Your Health — Limitations of BMI
Body mass index, often abbreviated as BMI, is one of the measures of one’s health and obesity. By calculating this, you can estimate one’s risk of cardiovascular disease, type II diabetes, gallstones, high blood pressure, etc. We all heard about it and learned about our values when we go to hospitals for medical check up or gyms.
However, there is a limitation in BMI. It does not accurately tell you about your health. In fact, it sometimes can tell you opposite result for certain populations. In this post, I would like to discuss some limitations of BMI and ways to properly use it!
Let’s do some calculations. BMI is calculated by your body weight (kilograms) divided by your height (meters) squared. Try calculating it using your calculator! (Or, use this.) Then, see where your body weight falls under in the chart.
Underweight: Less than 18.5 kg/m^2
Normal weight: 18.5–24.9 kg/m^2
Overweight: 25–29.9 kg/m^2
Obese: 30 kg/m^2 or greater
Were you shocked by your number? Not satisfied? I am sure most of you did. But, let me tell you a good news. Again, there is a limitation of BMI, especially if you are someone who exercises frequently.
At a given size, your muscle weighs more than fat. So, it is possible for a muscular and fit person to have with same height and weight with overweight person with higher fat and less muscle. Not clear enough? Take a look at the picture below.
BMI higher than 30 is classified as ‘Obese’, which should mean someone with BMI of 33.9 kg/m^2 is likely to have high risk of having one of the diseases mentioned.
But, it is hard to say that the person on left is unhealthy. He actually seems very healthy. That is the limitation of BMI. For fit individuals and athletic population who have muscular build, BMI overestimates their body fat. Thus, it is not only an inaccurate way of measuring their health but also can tell you opposite results.
It is not just true for athletic population. For older individuals with less muscle and higher body fat, it underestimates body fat.
Then, why are they still using BMI?
Though BMI is not useful when applied to single individual, it is useful for making inferences of large populations. Because only data needed are their average height and weight, it is very convenient way to have a general idea of health condition in large group.