ATLANTA -- Fit healthy people tend to have higher numbers of circulating cells that regenerate blood vessels, a new study shows.

A team of scientists measured the ability of 33 healthy middle-aged people of normal weight to withstand aerobic exercise. They also measured the levels of leptin, an inflammatory hormone produced by fat cells, and endothelial progenitor cells, which repair blood vessels by providing new cells that form blood vessels' linings, in study participants' blood.

Leptin sends satiety signals to the hypothalamus, part of the brain that controls appetite. Most obese people appear to produce an abundance of leptin, but for them, leptin's appetite-controlling effects are muted. High levels of leptin also have been associated with inflammation and vascular disease, study authors write.

“We have shown for the first time in a healthy population that increased fitness and reduced body fat are associated with higher levels of circulating progenitor cells,” says cardiology researcher Mick Ozkor, Emory University School of Medicine, who presented the data in late March at the American College of Cardiology's 57th Annual Scientific Session in Chicago. “Exercise may be the reason for the differences in regenerative capacity, even in apparently healthy individuals without risk factors.”