Is the obesity tide turning among preschoolers?

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.

Recent studies have shown that after decades of rising obesity rates among U.S. kids and teens, the numbers seem to be leveling off.

But less has been known about young children specifically, said Dr. Xiaozhong Wen, of Harvard Medical School and the Harvard Pilgrim Health Care Institute in Boston.

Patterns in that age group are important, Wen said, because they give a glimpse into the future of the national obesity problem.

So his team looked at obesity trends among kids younger than six who were seen at greater-Boston-area pediatric offices.

The researchers found that after holding steady between 1999 and 2003, the obesity rate began to fall after 2004.

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.

The rate among children younger than two, though, stayed steady at 9.5 percent.

The findings raise the possibility that young children in eastern Massachusetts may be "leading a new wave of better weight status," according to Wen.

Or that at least may be true of young children with private insurance, he said.

"We didn't see much change in children on Medicaid, unfortunately," Wen told Reuters Health. Medicaid is the government health insurance program for the poor.

Of Massachusetts children on Medicaid, 11.5 percent were obese in 2008, which was down from just over 12 percent in 2004.

Wen's team found a similar trend in a national database that tracks mostly low-income U.S. children. There, the obesity rate remained stable between 2004 and 2008 - at almost 15 percent among children between the ages of two and six.

It's not clear why obesity was generally less prevalent among Massachusetts kids versus the nation as a whole, Wen said.

But one reason, he noted, could be the higher percentage of Asian-American children in the Massachusetts study group. In addition, families in the state sample may have been higher-income versus the national average.