I often come across heated discussions online regarding the use of BMI measurements, the aggression is usually coming from the people who say it is completely useless and an irrelevant measurement of whether you are a healthy weight or not. So I’ve decided to give a definitive guide to BMI and a rational view as to how useful or useless it might be.
First things first:
What is BMI?
BMI is the Body Mass Index.
What is it Used for?
BMI records an individual’s height and weight to give an indication of whether they are a healthy weight or not.
How do you get a Persons BMI?
You need to measure a persons Body Weight in KG and Their Height in meters. The BMI formula is:
Weight in KG divided by the Persons Height in Meters Squared!! (So if they are 1.75 meters you need to Multiply this by itself to get it as Meters Squared). The number you get can then be looked up on the BMI scale.
What Does the Number Mean?
If the number is between 18.5 – 24.9 you are a Healthy Weight. Below 18.5 = Underweight, 25 and above = Overweight while 30 and above = Obese.
Is BMI an Accurate Indicator as to whether a person is overweight or not?
NO it is not! It does not differentiate between Fat Weight and Muscle Weight so it is not accurate with muscular individuals. BMI only takes into consideration a person’s Height and their Weight. It doesn’t take into consideration their body composition. Therefore a well-trained, well built, fit, healthy rugby player can have a BMI that would tell us he is Obese but when looking at him this is clearly not the case. This is because the majority of his weight is made up of lean muscle and not body fat. This person doesn’t need to lose weight to get down to a healthy BMI of 18.5 – 24.9 to be considered a Healthy weight.
So BMI is completely useless so?
NO!! This is where The Rational Debate starts. BMI is an irrelevant form of measurement for athletes, sports people, body builders, rugby players or basically anyone who is physically active and as a result will have a high level of muscle mass and low-level of body fat. So when dealing with these people you can pretty much throw BMI out the window as a tool for assessing a persons healthy weight. You really need to measure these people using Skin-fold measurements or ideally specialist equipment to get their Body Fat Percentage.
This doesn’t mean BMI measurements do not have their place in the fitness world or that they are a useless tool for helping people get to a healthy weight.
When I first started trying to lose weight in Jan 2012 I was 3 stone overweight. I downloaded an app and when I keyed in my details I was shocked to realise I fell into the Obese bracket on the BMI scale as my BMI was over 30 (30.09). I hadn’t exercised in years, my weight gain was down to a very poor diet consisting of fried foods, too much alcohol, junk food and a complete lack of exercise. Was this BMI reading an accurate recording that I needed to lose weight? it certainly was. Unlike the Rugby player I spoke of earlier my weight was mostly down to Body Fat Weight and not Muscle Weight. I was basically too heavy for my height. Getting down to a Healthy BMI was an important motivating factor for me and to see this number reducing was a massive boost to me when I found training hard. BMI had a very important role in helping me lose weight and to get more involved with exercise and fitness.
So In Summary
No BMI is not an accurate measurement of a person’s health but it is for people who are inactive or sedentary like I was. It is very simple to understand and to calculate so this is an advantage of using the BMI scale. As a rule of thumb, if you are an active person who likes to exercise and tries to eat well, then don’t beat yourself up if your BMI number is too high chances are this is down to the muscle you have gained through exercise. On the other hand, if you have been out of the exercise game for a while and you think you may need to lose some weight and your BMI is telling you that you are overweight, chances are you need to lose some weight.
Sometimes people can be very quick to ram their knowledge of something down your neck and tell you what you think is wrong. Sometimes they can be blinded by this. I believe in fully understanding a topic and being able to view it from both sides. Exercise and Health Fitness is an area I really enjoy studying and I know that there is no one way to be fit or healthy so there is always a rational way to look at any aspect of fitness and figure out for yourself if this fits into what YOU believe in.
Kind Regards.
Phil
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