What Is Your BMI?

You’ve probably heard about BMI – at the doctor’s office, in gym class, on the news, in a magazine. BMI stands for Body Mass Index, and it’s become the latest tool to determine whether or not a person’s weight is in a healthy range. When BMI was developed, it wasn’t actually meant to be used to classify people’s weight or make a medical diagnosis—but that’s exactly what has happened!

Here’s how BMI works: it calculates the percentage of body fat a person has in relation to their height and weight. Sounds simple. The problem is that BMI doesn’t give a realistic ration of body fat when a person is very tall, very short, very muscular, or from certain ethnic groups. And BMI is not meant to be used for children who have growth spurts regularly because they often gain weight prior to shooting up in height.

The BMI is used in a different way with children than it is with adults. For children, BMI works on averages, which means a group of children are weighed and their weights are added together then divided by the number of children in the group. So if you have ten children in a group and four weigh 70 lbs., two weigh 90 lbs., one weighs 105 lbs., and three weigh 87 lbs., the total of their weights is 826 lbs. When you divide that number by ten (the total number of children), you find that the average weight of the children in the group is 82.6 lbs. According to BMI usage, that would mean anyone below 82.6 lbs. would be considered underweight and anyone over 82.6 lbs would be considered overweight. Pretty straightforward, right?

Wrong. The BMI is actually completely arbitrary when used with children. If you measure a group of children who all weigh over 150 lbs., the average weight will be much higher than if you measure a group of children who all weigh less than 100 lbs. So, in reality, this will not tell you whether you are underweight or overweight, as there will never be a group where everyone is exactly the same weight.

So the next time you’re at the doctor’s office or in gym class and it’s time to calculate your BMI, remember that the result doesn’t really mean that much. BMI is just a number. It is much more important to focus on healthy nutritional intake, engaging in exercise or movement that you enjoy, and being happy than some arbitrary number.

Bri King

About the Author

Bri King

What Is Your BMI? Bri King You’ve probably heard about BMI – at the doctor’s office, in gym class, on the news, in a magazine. BMI stands for Body Mass Index, and it’s become the latest tool to determine whether or not a person’s weight is in a healthy range. When BMI was developed, it wasn’t actually meant to be used to classify people’s weight or make a medical diagnosis—but that’s exactly what has happened! Here’s how BMI works: it calculates the percentage of body fat a person has in relation to their height and weight. Sounds simple. The problem is that BMI doesn’t give a realistic ration of body fat when a person is very tall, very short, very muscular, or from certain ethnic groups. And BMI is not meant to be used for children who have growth spurts regularly because they often gain weight prior to shooting up in height. The BMI is used in a different way with children than it is with adults. For children, BMI works on averages, which means a group of children are weighed and their weights are added together then divided by the number of children in the group. So if you have ten children in a group and four weigh 70 lbs., two weigh 90 lbs., one weighs 105 lbs., and three weigh 87 lbs., the total of their weights is 826 lbs. When you divide that number by ten (the total number of children), you find that the average weight of the children in the group is 82.6 lbs. According to BMI usage, that would mean anyone below 82.6 lbs. would be considered underweight and anyone over 82.6 lbs would be considered overweight. Pretty straightforward, right? Wrong. The BMI is actually completely arbitrary when used with children. If you measure a group of children who all weigh over 150 lbs., the average weight will be much higher than if you measure a group of children who all weigh less than 100 lbs. So, in reality, this will not tell you whether you are underweight or overweight, as there will never be a group where everyone is exactly the same weight. So the next time you’re at the doctor’s office or in gym class and it’s time to calculate your BMI, remember that the result doesn’t really mean that much. BMI is just a number. It is much more important to focus on healthy nutritional intake, engaging in exercise or movement that you enjoy, and being happy than some arbitrary number. Image © Tamas Panczel - Eross \| Dreamstime.com
About the Author Bri King Bri King is an Australian counsellor and social worker. She is staunch advocate of Fat Acceptance, supporter of Health at Every Size and blogs at www.fatlotofgood.org.au. Bri also works in the areas of academic research and does wedding photography on the side.