Your son is a little chubby, but he's only 8 years old. Should you be concerned?

Well, yes. Parents need to take action if a child is overweight or bordering on it. Diseases linked to excess body fat such as diabetes and high blood pressure are showing up in children at much younger ages today. And older children and teens who are overweight or obese are likely to stay that way as adults.

Today, close to one in five children and teens are dangerously obese. How do you know if your child's weight is a health risk? The Centers for Disease Control (CDC) created the Body Mass Index (BMI) for kids, ages 2 to 20. This screening tool compares the body fatness of your child to other kids the same age and gender.

Doctors now recommend that all children get a BMI reading at least once a year starting at age 2.If your child's BMI is very high or low, your doctor may suggest changes in your child's diet or activity level to get him or her back on a healthier track.

Calculating BMI
Finding out your child's BMI starts with an accurate height and weight measurement. Your doctor will check this against the BMI-for-age growth chart to come up with a percentile ranking. This ranking shows how your child's BMI compares to other children's. If your child is in the 85th percentile, for example, this means that 85 percent of children of the same age and gender have a lower BMI.

These CDC standards can help your doctor further assess your child's health risks related to weight:

• Underweight: Lower than the 5th percentile
• Healthy weight: 5th percentile to lower than the 85th percentile
• Overweight: 85th percentile to lower than the 95th percentile
• Obese: 95th percentile or higher

It's important to remember that BMI is only a screening tool, though. Other factors influence whether a child's weight is considered healthy or not.

Not an exact science
BMI is usually an effective way to monitor your child's weight, but it doesn't tell the whole story. Some doctors like to measure BMI twice a year to observe the child's growth pattern. This lets you see any significant up or down movement in the BMI-for-age percentile.

Being in a very high or low percentile is not always a problem, either. Your child's fitness level counts, too. Very athletic children may have a high BMI number due to extra muscle mass - not excess body fat.

Likewise, children with a BMI below the 10th percentile do not necessarily have a medical problem or eating disorder. Some children are just thin.

For all these reasons, your doctor is the best source for determining whether your child is at a healthy weight - not a BMI chart.

Related Articles Sensitive Ways to Deal With Your Child's Weight Problem Your Child Should Have an Annual Physical Before School Starts Keeping Your Child Healthy: The Latest Guidelines for Well-Child Visits Help Kids Stop Overeating Children and Rising Obesity Rates: A Chronic Problem Why It's Important to Know Your BMI (Body Mass Index)

External Sources Rao G. Childhood obesity: highlights of AMA Expert Committee recommendations. American Family Physician. 2008;78(1):56-63.. Accessed August 26, 2009 Baylor College of Medicine, Children's Nutrition Research Center. Children's BMI-percentile-for-age calculator. . Accessed August 26, 2009 Centers for Disease Control. About BMI for children and teens. . Accessed August 26, 2009 National Heart Lung and Blood Institute. How are overweight and obesity diagnosed? . Accessed August 26, 2009

This article was reviewed and updated 08-01-2009.