We see the words "overweight" and "obesity" a lot. You might use them yourself (maybe you told your best friend something like, "I'm overweight; I need to drop 5 pounds before prom.")
So it may surprise you that these words actually have a medical meaning. Doctors use them to define the amount of extra fat a person is carrying.
A doctor likely wouldn't call someone who wants to lose 5 pounds before prom "overweight." When a doctor says a person is overweight or obese, it's serious. Being overweight or obese increases the risk of health problems like diabetes and high blood pressure.
How Do Doctors Define Overweight?
Health care professionals use a measurement called body mass index (BMI) to figure out if a person is overweight. BMI is a calculation that uses your height and weight to estimate how much body fat you have.
After calculating your BMI, a doctor or nurse will plot the result on a BMI chart. This allows health professionals to compare your growth with other teens who are the same age and gender to see where you fit in.
BMI changes with age. That's why doctors should plot and follow BMI over time. There are also different charts for girls and guys.
The growth charts have lines for "percentiles." Like percentages, percentiles go from 0 to 100. Eight lines on the BMI growth charts show the 5th, 10th, 25th, 50th, 75th, 85th, 90th, and 95th percentiles. The 50th percentile line is the average BMI of the teens who were measured to make the chart.
When your BMI is plotted on the chart, the doctor can see how you compare with teens the same age and gender as you. Based on where your number plots on the chart, the doctor will decide if your BMI is in the underweight, healthy weight, overweight, or obese range.
There's a big range of normal on the chart: Anyone who falls between the 5th percentile and the 85th percentile is a healthy weight. If someone is at or above the 85th percentile line on the chart (but less than the 95th percentile), doctors consider that person overweight. A BMI measurement over the 95th percentile line on the chart puts someone in the obese range.
Why Does It Matter?
A couple of extra pounds are not a health risk for most people. But being overweight or obese can lead to health problems, both physical and emotional.
It's particularly important to catch weight problems while someone is still a teen. Being overweight as a teen makes a person more likely to be overweight as an adult. In addition, many overweight teens are developing long-term medical problems like diabetes. Teens who are overweight also might be teased or bullied and are more at risk for depression.
If your doctor thinks your weight isn't in a healthy range, he or she will probably make specific eating and exercise recommendations or refer you to a dietitian or doctor who specializes in weight management.
Doctors can help people take a healthy approach to losing weight. Fad diets and other weight-loss methods can be hard to stick to, may not provide the nutrients your body needs, can have unwanted or dangerous side effects, and are usually not effective in the long run.
Losing weight can be challenging. But it's a lot easier to turn things around if you catch weight problems early on.