When exercise hurts the bones

Children who are overweight face more than future health problems. They appear more likely to have broken bones and joint problems during childhood than kids of normal weight.

“A lot of people think that if you’re an overweight kid ... that later on in life you’re going to run into having heart disease or Type 2 diabetes,” said Dr. Susan Yanovski, director of the obesity and eating disorders program at the National Institute of Diabetes and Digestive and Kidney Diseases.

“But kids and adults who are overweight are already having problems with their mobility, fractures and joint pain,” Yanovski said.

A study led by her husband, obesity researcher Dr. Jack Yanovski, found that children and teens who were overweight were far more likely to have had a fracture than their ideal-weight peers. They also had more bone and hip joint abnormalities, which can lead to permanent deformities.

The research involved 227 overweight children and adolescents and 128 who weren’t overweight. The children’s average age was 12. All were enrolled in various federal health studies between 1996 and 2004.

A review of their medical history revealed that 13% of overweight kids had had at least one broken bone at some point, compared with less than 4% of ideal-weight children.

Similar results were found for how many had muscle, bone or joint pain, especially knee pain, and restricted movement.

“The combination of musculoskeletal pain and poor mobility may possibly lead to less physical activity ... and perpetuate the vicious cycle,” said Jack Yanovski, head of the growth and obesity program at the National Institute of Child Health and Human Development.

He presented results of the study at a recent meeting of the Obesity Society in Vancouver, British Columbia.

Caleb Ezzard knows the problem well.

With 362 pounds on his 5-foot, 4-inch frame, the 14-year-old from Louisville, Ky., developed Blount’s disease, a growth disorder of the shin bone that causes the lower legs to bow inward.

“I used to play football,” but the bone problem put an end to that, he said. “When I would run, my weight would put pressure on my leg and my bones would start moving and it would hurt.”

Even more common than Blount’s is SCFE, or slipped capital femoral epiphysis, caused by improper growth in the ball part of the ball-and-socket joint that forms the hip, said Dr. Junichi Tamai, a pediatric orthopedic surgeon at Children’s Hospital Medical Center in Cincinnati.

Children often say their knees hurt, but the real problem is the malformation that’s starting to occur in the joint, he said. Being unable to exercise makes the situation worse.

“If a child is very active, chances are the bones are very strong,” because weight-bearing exercise promotes bone density, Tamai said.

“Also, a very active child may be able to fall better,” he said. If kids have too many pounds on their frame, “when they fall, there’s just more weight behind it” and bones are more likely to snap.

Hormones are believed to play a role too.

“What we generally see is that lean, muscular young men have the hardest bone, and that goes along with the testosterone,” which can be lower in very overweight boys, Tamai said.

In Caleb’s case, orthopedic surgeries could only partly resolve the leg issues. In October, he had obesity surgery, hoping to get at the underlying problem.

His weight is starting to drop, but he won’t be able to consider much exercise until it falls some more.

“It’s painful to walk,” he said.