What Should A 14-year-old Boy's Body Mass Index Be?

Changes such as increases in muscle and bone mass cause normal weight and height gains in teen boys. However, teens' bodies change at different times, so at age 14 you may be the same height as a friend but weigh a very different amount. Your doctor can help you assess your health by using a tool called body mass index, or BMI. This estimates how much fat you have on your body based on your weight and your height.

Healthy Weight Categories

Your doctor will calculate your BMI by squaring your height in inches, dividing it into your weight in pounds, then multiplying the result of that equation by 703. The resulting number is considered your BMI score. Although this number properly estimates a grown adult's body fat, it isn't as ideal for you when you're a teen because your body fat levels are consistently changing and because body fat levels are different between boys and girls. That's why doctors use a tool called BMI-for-age growth charts.

Charts

Your doctor will plot your BMI score onto a chart for all 14-year-old boys in order to tell you where your BMI fits in. You're generally considered underweight if your BMI is under the 5th percentile, but you're at a healthy weight if your number is at the 5th percentile all the way to right below the 85th percentile. You may be overweight if you're at the 85th percentile but under the 95th percentile, or obese if you're at or higher than the 95th.

Standard Ranges

You can get a solid idea of where your BMI fits in with your peers' BMIs by looking at the Center for Disease Control's 2000 Body Mass Index for Age tables. According to the table for 14-year-old boys, you might be around the 5th percentile if your BMI score is between 16 and 16.6, right at the average 50th percentile if your score is from 19.16 to 19.8 and around the 85th percentile if your score is between 22.7 and 23.4.

Considerations

Your BMI doesn't tell the whole story about your weight and health. For example, you may have a low BMI if you're simply a late bloomer or a high BMI if you're very muscular. Your doctor would have to do some tests and ask you some questions about your eating and exercise habits to fully determine whether excess fat could be a problem for you.

What Comes Next

Your doctor might give you special exercise and diet recommendations if she thinks your weight should go down a bit. Focus on her advice rather than trying any pills or fad diets; your body is still growing a lot and it needs calories to develop properly. If your BMI is on the low end of the scale, chances are you're just growing at a different pace than your peers. However, be sure to let your doctor know if you've experienced any symptoms such as fatigue, diarrhea or cough for at least a week.