The BMI is a screening tool used by your health care provider to determine your risk for numerous health problems. BMI is interpreted differently for children and adults. Although they both start with a formula involving weight and height, children's BMI is ranked in a percentile based on large samples of children matched by age and sex. A boy is considered overweight when he ranks in the 85th to 95th percentile. Talk to your child's health care provider about how to deal with being overweight in childhood, especially in boys, as their levels of body fatness change sometimes dramatically as they grow.
The Body Mass Index
The body mass index, or BMI, tells you about your weight in relation to your height. The formula for it is your weight in kilograms divided by the square of your height in meters or your weight in pounds divided by your height in inches squared and multiplied by 703. BMI is a tool used by health care providers to determine your risk of obesity and other diseases. As an acknowledged imperfect tool, it's a handy initial calculation your doctor makes to assess your level of body fatness. Invented in 1832 by a Belgian astronomer, BMI has always had its share of critics. For example, it doesn't distinguish well between overweight people and those with high amounts of lean muscle. Adult BMI also doesn't take into account age or gender. But public health officials from the World Health Organization to the Centers for Disease Control and Prevention --- and the American Academy of Pediatrics --- accept its use as a primary screening tool but not as a diagnostic tool.
BMI in Children
The measurements used in describing BMI in children differs from those used for adults. According to the CDC, after your child's health care provider calculates BMI, he will plot the resulting number along a growth chart. The CDC's Clinic Growth Charts are based on a number of body measurements in representative samples of children. They have been widely used since 1977. The end result is a BMI percentile ranking for children. It tells where your child falls in terms of size and growth in relation to larger patterns of sampled children of the same age and sex. That ranking helps your child's health care provider know whether he is underweight, a healthy weight, overweight or obese.
Overweight Boys
A boy is considered overweight when he falls between the 85th and 95th percentile in the CDC's BMI-for-age growth charts. As an example, a 10-year-old boy with a calculated BMI of 21 would not be considered obese by adult standards, but children's rankings are interpreted differently. He would fall just above the 90th percentile on the CDC Growth Charts. Know too that levels of body fat change as children age, and as they grow, different patterns in body fat develop between boys and girls. It's important to ensure your pediatrician monitors your child's weight and health status as he grows.
Consequences of Being Overweight
In addition to poor body image, low self-esteem and bullying, overweight children can suffer some very adult-like health consequences for being overweight. For example, obesity, glucose intolerance and insulin resistance, high blood pressure, fatty liver and sleep apnea are being seen at much earlier ages. Too much body fat in boys may also delay the onset of puberty, according to a report by ScienceNews. According to the White House Task Force on Childhood Obesity the problem may even pose a national security challenge. Children who are overweight tend to become adults who are overweight, and in 2010 when the task force issued its first report, more than 25 percent of Americans ages 17 to 25 were unfit for military service because of their weight.
References
- "Healthy Weight Journal"; Normal Weight Gain in Growing Children; Robert Malina; May/June 1999
- Centers for Disease Control and Prevention: Body Mass Index: About BMI for Children and Teens
- Slate; Beyond BMI: Why Doctors Won't Stop Using an Outdated Measure for Obesity; Jeremy Singer-Vine; July 20, 2009
- White House Task Force on Childhood Obesity: Solving the Problem of Childhood Obesity within a Generation; May 2010
- ScienceNews; Body Fat Linked to Late Puberty in Boys; Janet Raloff; Feb. 2, 2010
- American Academy of Pediatrics: About Childhood Obesity
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