Increased exercise improved bone turnover, insulin sensitivity, adiposity in obese children

Twelve weeks of rigorous exercise resulted in stronger bones, improved insulin sensitivity and less visceral fat among obese children enrolled in after-school exercise programs, researchers from Georgia Health Sciences University reported in a new study.

According to Norman Pollock, PhD, assistant professor of pediatrics at the university, results also indicated that blood levels of osteocalcin may be a good indicator of bone turnover, insulin sensitivity and adiposity.

The study included 222 obese children aged 7 to 11 years who were randomly assigned to no-exercise control condition (n=78), low-dose aerobic exercise (20 minutes/day; n=71) or high-dose aerobic exercise (40 minutes/day; n=73). An oral glucose tolerance test was used to assess insulin sensitivity, bone formation, procollagen type 1 amino propeptide and bone resorption at baseline and post-test. DXA and MRI were used to measure total fat mass and visceral adipose tissue at baseline and post-test.

Pollock and colleagues reported a significant dose-response to exercise in bone formation (total osteocalcin), procollagen type 1 amino propeptide and insulin sensitivity with exercise (P<.04 for all). This was also true for fat mass and visceral adipose tissue; the researchers observed significant downward trends (P<.04 for both). There was no dose-response effect of exercise on bone resorption (carboxyterminal telopeptide region of type I collagen), the researchers wrote.

These data earned Pollock the 2011 American Society for Bone and Mineral Research Young Investigator Award.

"The idea is that bones can possibly sense environmental stimuli such as being physically active or sedentary and dictate energy regulation accordingly," Pollock said in a press release. "When osteocalcin is released in your blood, that hormone is talking back to the adipocytes, the cells that store fat, and the pancreatic cells that release insulin to improve energy metabolism."

According to Pollock, bone and fat cells have a common ancestry: They are both derived from mesenchymal stem cells.

"It's possible that children's early lifestyle habits and experiences may induce alterations in body composition and predispose them to a lifetime of obesity," he said in the release. "As parents, we must ensure that our children balance out their screen time with enjoyable physical activity."

Disclosure: Dr. Pollock reports no relevant financial disclosures.

For more information:

Pollock N. Concurrent oral session. Abstract #1177. Presented at: the American Society for Bone and Mineral Research 2011 Annual Meeting; Sept. 16-20; San Diego.

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