Not too long ago, a reader wrote in telling us that her 10-year-old came home from school with a body mass index (BMI) report that said he was obese. "But he looks fine to me," she said. Which begs the question: How accurate is BMI in kids? Childhood obesity researcher David Kaelber, MD, an internist and pediatrician at MetroHealth in Cleveland, explains how it all works, healthy BMI ranges and how parents can teach their kids healthy eating habits in the event that they may show early signs of easy weight-gain.
The 411 on BMIs
In children, BMI percentile is pretty accurate, Dr. Kaelber says. First, you take a child's height and weight, and calculate his BMI the same way you would an adult's. That number is then plotted onto the standard BMI growth chart, which compares his BMI to the BMI of other kids the same age and gender—giving you his BMI percentile.
Underweight = less than 5th percentile
Healthy weight = 5th to 85th percentile
Overweight = 85th to less than 95th percentile
Obese = 95th percentile or greater
For example, a 10-year-old boy who is 4'5" and weighs 95 pounds would have a BMI of 23.8, placing him above the 95th percentile (obese). Because these calculations involve several steps, it's easiest to figure out your child's BMI percentile by plugging the info into an online calculator, such as the one at Apps.Nccd.Cdc.gov/Dnpabmi.
"BMI percentile isn't perfect, but it's extremely rare that someone would fall into the obese category simply because he's muscular," says Dr. Kaelber. But with many Americans now overweight or obese, most of us have lost sight of what a healthy weight looks like. So be sure to discuss your child's BMI percentile with his pediatrician, and take the information seriously. "Parents often assume, 'My child will hit a growth spurt at puberty and that will solve the problem.' That's absolutely not true," says Dr. Kaelber. In fact, his research shows that children who are overweight or obese before puberty are about 20 times more likely to be overweight or obese after puberty.
Conditions like high cholesterol, high blood pressure, diabetes and fatty liver disease (when fat deposits accumulate in the liver) are more common in overweight and obese kids, so if your child is heavy, make sure his doctor screens him for them annually.
Healthy Eating Tips for Kids
Instead of putting kids on a "diet," which implies deprivation, help them adopt healthy habits, like the five below, that'll last.
1. Get them to help with prep. "Kids are more likely to eat what they've been involved in making," says Keith-Thomas Ayoob, EdD, RD, associate professor of pediatrics at Albert Einstein College of Medicine. In fact, that's the idea behind a new nonprofit campaign, The Kids Cook Monday. Toddlers can "paint" vegetables with olive oil; older kids can dice them. Learn more at TheKidsCookMonday.org.
2. Encourage volunteering. Boredom often goes hand-in-hand with overeating; volunteering keeps them busy and boosts self-esteem (which can help protect against disordered eating), says American Dietetic Association spokeswoman Melinda Johnson, RD.
3. Limit eating at the kitchen table. Munching while distracted (by a TV show, video game, etc.) leads to eating hundreds of extra calories, says Karen Ansel, RD, coauthor of The Baby & Toddler Cookbook.
4. Let them eat dessert. Indulging a little every day means kids won't feel deprived and will be less likely to overeat, says Elisa Zied, RD, author of Feed Your Family Right! Just remember to keep portions small.
5. Track it by texting. Research shows that kids are more willing to track their eating habits via texting than pencil and paper. If your child is struggling with his weight, suggest that he text himself every time he eats.
