Obese children as young as age 3 show signs of an inflammatory response that has been linked to heart disease later in life, researchers said, in a finding that is likely to further stoke concerns about childhood obesity.

The results suggest that obesity-related disease processes may start earlier than previously believed. Nearly 30% of obese 3-to-5-year-olds had elevated blood levels of C-reactive protein—a widely studied marker for inflammation—compared with 17% of healthy-weight kids of the same age. The disparities widened as children aged, according to the study, which is being published Monday in the journal Pediatrics.

“It’s really important to be concerned about childhood obesity and to even be concerned when they are quite young,” said Asheley Skinner, a professor of pediatrics at the University of North Carolina School of Medicine, who was the first author of the study. “We can’t wait until they’re adolescents or adults.”

In the U.S., 14% of 2-to-5-year-olds are considered overweight, or at the 85th percentile or greater of weight for height in their age group.

C-reactive protein, or CRP, has been shown to help predict risk of heart disease, stroke and death under certain conditions, according to the American Heart Association. Previous studies have found that overweight and obese adults show elevated levels of CRP, but less has been known about CRP in children.

The study examined three markers that measure different aspects of inflammation, including CRP, in more than 16,000 children nationwide between the ages of 1 and 17. By ages 15 to 17, CRP was elevated in about 60% of obese teens, compared with 18% of teens of healthy weight. The increase was even more pronounced for very obese kids, with nearly 43% of young children and 83% of teens showing CRP elevation.

A similar pattern of elevation was observed for the other two inflammatory markers, though one of the markers wasn’t elevated in obese children until the age of 6.

It isn’t known whether elevated CRP in young children will predict heart disease in adulthood. Such a study, which would involve following overweight and obese children until adulthood, hasn’t been done, Dr. Skinner said. But, she said there wasn’t any evidence to suggest that CRP response would be different in children than in adults; its response in the body is the same regardless of age. Inflammation is the body’s immune response to infection or injury.

The concern of finding CRP elevation in such young children is that its effects could be cumulative. Future research is needed to investigate whether that is the case, and also whether losing weight could reduce CRP response in kids, according to Dr. Skinner. This study was funded by the National Institutes of Health.

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