"I'm 5' 11" and weigh 190 pounds. My basketball teammates all weigh less than me. Should I lose weight?"

"My friend is trying to lose weight and it worries me. She's 5' 2" and weighs 125 pounds. Is she too fat?"

"I'm 5' 4" and I weigh 95 pounds. I think I need to gain weight because I can see my ribs. What should I do?"

"What's the right weight for my height?" is one of the most common questions girls and guys have. It seems like a simple question. But, for teens, there's no single number that's the right weight. Why not? Because people have different body types. Some are more muscular, some are more developed. As teens go through puberty, the amount of muscle, fat, and bone in their bodies can change dramatically. Because muscle and bone weigh more than fat, a person's weight can vary quite a bit during this time. So it can be normal for two people who are the same height to have very different weights.

During puberty, the body begins making hormones that spark physical changes like muscle growth (particularly in guys) and weight gain in both guys and girls. Once these changes start, they continue for several years. The average person can expect to grow as much as 10 inches (25 centimeters) during puberty before he or she reaches full adult height.

All adolescents go through a period when they grow faster. Most guys and girls gain weight more rapidly during this time. All that new weight gain can be perfectly fine - as long as body fat, muscle, and bone are in the right proportion. Some teens, especially those who go through puberty on a later time schedule, may feel too skinny. The good news is that their growth, development, and weight gain almost always catch up to other people their age later on.

It can feel quite strange adjusting to suddenly feeling heavier or taller. So it's perfectly normal to feel self-conscious about weight during adolescence - a lot of people do.

The BMI formula uses height and weight measurements to calculate a BMI number. This number is then plotted on a chart. (There are different charts for guys and girls under the age of 20.) The chart tells a person whether he or she is underweight, average weight, at risk of becoming overweight, or overweight compared to other girls or guys the same age.

To figure out your BMI, you'll need an accurate height and weight measurement - so if you don't have a lot of confidence in your bathroom scale, get weighed and measured at your doctor's office or school. Enter your height and weight into this calculator and then hit "calculate." To find out what the number means, go to the BMI chart.

What's Your BMI? Instructions: 1. Enter your height and weight. 2. Click "calculate" to get your BMI. 3. Go to the BMI chart. English Calculation Height:   feet and   inch(es) Weight:   pounds Your BMI:   Metric Calculation Height:   meters Weight:   kilograms (Please note: 1 Meter = 100cm) Your BMI:

With this number in hand, a doctor finds out where a teen falls on a BMI chart.

Figuring out the body mass index is a little more complicated for teens than it is for adults (that puberty thing again). BMI charts are based on a person's percentile. A percentile is a way to compare one individual to a group of people.

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 allow the person to make changes in diet and exercise before he or she goes on to develop a weight problem.

Although BMI can be a good indicator of a person's body fat, it doesn't 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.

If your doctor has a concern about your height, weight, or BMI, he or she may ask questions about your physical activity and eating habits. Your doctor may also ask about your family background to find out if you've inherited traits that might make you taller, shorter, or a late bloomer (a person who develops later than other people the same age). The doctor can then put all this information together to decide whether you might have a weight or growth problem.

If your doctor thinks it's a good idea for you to control your weight, you will probably get specific dietary and exercise recommendations based on your individual needs. Following a doctor's or dietitian's plan that's designed especially for you will work way better than following fad diets. For teens, fad diets or starvation plans can actually slow down growth and sexual development.

What if you're worried about being too skinny? Most teens who weigh less than other teens their age are just fine. They may be going through puberty on a different schedule than some of their peers, and their bodies may be growing and changing at a different rate. Most underweight teens catch up in weight as they finish puberty during their later teen years and there's rarely a need to try to gain weight.

In a few cases, teens can be underweight because of a health problem that needs treatment. If you feel tired or ill a lot, or if you have symptoms like a cough, stomachache, diarrhea, or other problems that have lasted for more than a week or 2, be sure to let your parents or your doctor know. Some teens are underweight because of eating disorders, like anorexia or bulimia, that require attention.

It can be tough dealing with the physical changes our bodies go through during puberty. But at this time, more than any other, it's not a specific number on the scale that's important. It's keeping your body healthy - inside and out.