WASHINGTON, Aug 15, 2010 (AFP) - Obesity rates among African-American girls have risen in the past decade, stagnated among Hispanics and dropped among whites, a study published Monday said.

Researchers looked at health data gathered between 2001 and 2008 for more than eight million fifth, seventh, and ninth-grade students - kids aged around eight to 17 - in California.

They found that black, Hispanic and American Indian girls were two to three times more likely than non-Hispanic white girls to have high body mass indices, the measure of overweight and obesity, the study published in the journal Pediatrics found.

White girls were the only ones in their gender group to see obesity rates drop back to 2001 levels, the study led by Kristine Madsen of the University of California, San Francisco's department of pediatrics found. Among Hispanic girls, obesity rates stagnated.

And among black and American Indian girls, obesity rose.

American Indian girls showed the biggest percentage increases in obesity prevalence between 2001 and 2005, and no decrease afterwards. Black girls were not far behind in terms of percentage increases.

When it came to boys, the rate of obesity fell or leveled off for every group, but only non-Hispanic white boys' obesity prevalence fell back to 2001 levels after peaking in 2005.

The authors said the findings of their study concur with what several other recent studies have shown - that there are disparities in obesity prevalence along racial/ethnic lines.

They also found that the biggest percentage increases in obesity were among the most obese children.

Obesity leaves adults and children at greater risk for maladies ranging from high blood pressure to diabetes, heart disease and stroke than their healthy-weight counterparts, and obese children have been shown in a study to be at greater risk of dying prematurely of any cause than normal-weight kids. And the more obese the person, the greater the health risks.

The study findings "are a call to action for policies and interventions that are tailored for use in high-risk populations," the study said, while taking pains to stress that concerns about obesity apply to all youth.

"Reversing childhood obesity will require concerted public health efforts," the study authors said, suggesting that childhood obesity be attacked with the same arsenal as has been used to reduce smoking in the United States.

That could include a tax on sugary drinks; restricting advertising of unhealthy products in schools and during children's television programs; having more and better physical education programs; and banning the sale of high-fat and high-sugar products in schools, they said.

Childhood obesity is defined by which percentile a child fits into on a scale of body mass index (BMI) - weight in kilograms divided by height in meters squared - calculated for children by the Centers for Disease Control and Prevention.

A child with a BMI greater than or equal to the 85th percentile is considered overweight, while a child at or above the 95th percentile is considered obese.