A new study finds some obese children have elevated levels of a protein that can be an early warning sign of heart disease in adults.

C-reactive protein is an indication of inflammation in the body, and, at high levels, is considered an early sign of future heart disease.

"It's a risk factor in a similar way that elevated cholesterol is a risk factor for heart disease," says Asheley Skinner, a scientist at the University of North Carolina School of Medicine.

Obese adults can have high levels of C-reactive protein. Now, after analyzing data from a large national health and nutrition survey, Skinner reports finding similarly elevated levels in obese children as well, some as young as 3 years old.

Fat unhealthy at any age

Although most adults understand that being obese is not good for them, Skinner says many don't realize that it is also unhealthy for children to be overweight. "Even in these young kids," she points out, "when they're overweight, there's something different about their bodies. Their bodies are already producing things that could, long term, be damaging to them, even when they're really young."

A child's weight and levels of C-reactive protein are strongly related, and Skinner says this correlation increases as a child grows older. "The strength of this relationship between obesity and inflammation is concerning, that something's happening that could be cumulative."

Often parents don't realize there's a problem because their child does not look fat. But in a small, short person, Skinner says, just 3 kilograms can make the difference between a healthy weight and obesity. She adds that, since a lifetime of obesity may put a child at greater risk for heart disease and other health problems, parents need to be concerned about their child's weight from the very start.

Skinner's study appears in the journal "Pediatrics."