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Experts have developed a way to help figure out if a person is in the healthy weight range for his or her height, which is called the body mass index, or BMI for short. Body mass index is a formula that doctors use to estimate how much body fat a person has based on his or her weight and height.
The BMI formula uses height and weight measurements to calculate a body mass index number. This number is then plotted on a chart, which tells a person whether he or she is underweight, average weight, at risk of becoming overweight, or is already overweight. Figuring out the body mass index is a little more complicated for teens than it is for adults. BMI charts for teens use percentile lines to help individuals compare their body mass index to those of a very large group of people the same age and gender.
There are different body mass index charts for guys and girls under the age of 20. A person’s BMI number is plotted on the chart for their age and gender. Each body mass index chart has eight percentile lines for 5th, 10th, 25th, 50th, 75th, 85th, 90th, and 95th percentiles. A teen whose BMI is at the 50th percentile is close to the average of the age group, where teen above the 95th percentile is considered overweight.
This is because 95% of the age group has a BMI that is lower than the one he or she has. A teen whose BMI sits below the 5th percentile is considered underweight, because 95% of the age group has a higher body mass index. To figure out your BMI, you could use the tools below. Before you start, you will need an accurate height and weight measurement. Bathroom scales and tape measures are not always precise, so the best way to get accurate measurements is by being weighed and measured at your doctor’s office or at school.
What does BMI tell us?
Although you can calculate BMI on your own, it's a good idea to ask your doctor, school nurse, or fitness counselor to help you figure out what it means. That's because a doctor can do more than just use BMI to assess a person's current weight. He or she can take into account where a girl or guy is during puberty and use BMI results from past years to track whether that person may be at risk for becoming overweight.
Spotting this risk early on can be helpful because the person can then make changes in their diet habits and exercise routine before he or she goes on to develop weight problem. People do not like looking overweight, but weight problems get more serious than just how a person looks.
People who are overweight as teens increase their risk of developing health problems, such as diabetes or high blood pressure, both later in life and right now. Being overweight as a teen also makes a person more likely to be overweight as an adult and adults who are overweight may develop other serious health conditions, such as heart disease.
Although BMI can be a good indicator of a person’s body fat, it does not always tell the full story. Someone can have a high BMI because he or she has a large frame or a lot of muscle, like a bodybuilder or athlete, instead of excess fat. Likewise, a small person with a small frame may have a normal BMI but could still have too much body fat, so these are other good reasons to talk about your BMI with your doctor.