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What Does Body Mass Index Mean for Teens?

teen looking at scale

As you grow, your body keeps changing. That's why every time you go for a checkup the nurse checks your weight and your height. She's measuring to see how much you've grown -- and she may be using those numbers to figure out your body mass index, or BMI.

BMI is one way to measure how much body fat you have. Doctors check it because weighing too much for your height can lead to health problems like heart disease, diabetes, and high blood pressure.

Your doctor uses your age, gender, height, and weight to look at a growth chart to figure out your body mass index. You can also use an online teen BMI calculator to look it up yourself.

Teens need to use a "pediatric BMI calculator," different from the ones adult use, and their BMI is expressed in percentiles.


How You Compare to Other Teenagers

Teen BMI percentiles show how your weight compares to people who are the same age and gender as you. For example, a girl with a 75th percentile BMI is heavier than 75 out of 100 other girls her age.

The percentiles fall into four ranges:

  • Underweight: 0 to the 4th percentile
  • Healthy Weight: 5th percentile to 85th percentile
  • Overweight: 86th percentile to 95th percentile
  • Obese: 96th percentile to 99th percentile

Experts say the numbers are fairly accurate, especially with heavier teens. In some cases they can be misleading, though. Athletic teens, for example, may fall into the overweight category, when actually it’s more muscle that makes them weigh more.

After your doctor figures out your BMI, she may follow up by asking questions about what you eat and how much you exercise. Those details help her figure out the next best step if you're in an underweight, overweight, or obese BMI percentile.

A Healthy Body Mass Index

Your body may still be growing and changing, so the BMI you have now most likely won't be the one you'll have your whole life. You may still be going through growth spurts, and your height and weight are likely to change. As that happens, your BMI will change, too.

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