Six million U.S. kids are severely overweight, says Jack A. Yanovski, MD, PhD, head of the growth and obesityobesity unit at the NIH National Institute of Child Health and Human Development. These kids suffer more bone, joint, and muscle problems than normal-weight kids.
How much more? Yanovski's research team took a close look at 227 extremely overweight children and teens -- that is, they were among the heaviest 5% of kids for their age and sex. They compared their self-reported pain, mobility problems, and bone scans to those of 128 normal-weight kids.
And the researchers also saw a bone deformity in the overweight kids. Their lower legs didn't line up right with their upper legs. This happened most often in the very heaviest children and teens.
"An inward- or outward-pointing lower leg was more likely to happen the heavier children became," Yanovski says. "The deformity we saw makes it less likely for adolescents, once overweight, to move around. It can affect gait, and can lead to pain in the knee and, ultimately, arthritisarthritis and other problems in the knee joint."
Yanovski and colleagues report the findings in the June issue of Pediatrics.
A Vicious Cycle
You'd think active, healthy kids -- the ones playing sports, climbing trees, and leaping before they look -- would be most likely to get broken bones. But severely overweight kids actually break bones more often. The reason: Their greater mass means a short fall puts much more force on an outstretched arm or twisted leg.
It's not only fractures and bone deformity that threaten overweight children. Yanovski's team found that these children and teens reported more muscle pain, and more mobility problems, than normal-weight kids.
"Bone, muscle, and joint problems are particularly troubling in this age group," NIH Director Elias A. Zerhouni, MD, says in a news release. "If overweight youth fail to attain normal weight, they will likely experience an even greater incidence of these problems when they reach later life."
"At first sign of abnormal weight gain, doctors need to inform parents of the need to control their child's body weight," Yanovski says.
What about kids who already are severely overweight? Yanovski urges caution.
"Once kids have become severely heavy, parents and doctors have to think about giving them kinds of activity that don't stressstress the knee," he says. "Swimming and non-weight-bearing activities are appropriate. Running may not be realistic. Riding a bicycle would be better than running -- and in some cases even better than walking."