In eastern Massachusetts, the number of kids under age six who are obese declined significantly in recent years -- a trend that might be happening nationwide as well, according to a new study.

On the down side, obesity rates among lower-income children remain more stubbornly stable, researchers report in the journal Pediatrics.

By 2008, just under nine percent of boys were obese, compared with almost 11 percent between 1999 and 2004. Among girls, the obesity rate declined from over eight percent to just over six percent.

The trend was similar to what was going on nationwide at the time, the study found. But Massachusetts children had a lower obesity rate than the national norm, and the decline over time was sharper.

Based on federal health survey figures, just over 10 percent of two- to six-year-olds in the U.S. were obese in 2008. That was down from 14 percent in 2004.

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