MONDAY, Aug. 16 (HealthDay News) -- While some research suggests that the incidence of childhood obesity may be leveling off, a new study finds that for certain racial groups the rates may actually be getting higher.

The study, to be published in the September issue of Pediatrics, finds that black, Hispanic and American Indian girls have two to three times higher odds of having a high body-mass index (BMI) compared to white girls.

What's more, although rates of obesity peaked for Hispanic girls in 2005, they have kept on rising for American Indian and black girls.

"What was encouraging was that we saw some decline in obesity, [but] we saw an increase in the racial disparities. So, whatever policies we're putting in place probably aren't having the effect we want for all groups," said study author Dr. Kristine Madsen, an assistant professor of pediatrics at the University of California, San Francisco.

"Unfortunately, today's policies may be increasing the disparities in childhood obesity, and we need to target the communities that get left behind," she said.

Madsen and her colleagues reviewed data on more than 8 million fifth-, seventh- and ninth-grade students in California. The children underwent school-based screening of their BMI between 2001 and 2008.

Forty-six percent of the children were Hispanic, 33 percent were white, almost 13 percent were Asian, 8 percent were black and less than 1 percent were American Indian, according to the study.

The researchers separated the data into four BMI cut points for overweight and obesity: at or above the 85th percentile for age and sex (overweight), at or above the 95th percentile (obese), at or above the 97th percentile and over the 99th percentile (severely obese).

They found that 38 percent of the kids were overweight, nearly 20 percent were obese and 3.6 percent were severely obese.

Overall, boys were more likely than girls to have a high BMI for their age, according to the study.

For three of the four BMI cut points, the prevalence of obesity continued to increase through 2008 for black and American Indian girls. Among Hispanic girls, the rate of obesity leveled out after 2005. For white girls, rates of obesity peaked in 2005 and then declined to 2001 levels by the end of the study period. There were no increases in Asian girls.

The racial disparity was most evident in the highest BMI category. Just 1.3 percent of white girls fell into this category, but 4.9 percent of American Indian girls and 4.6 percent of black girls did, reported the study.

White boys peaked in 2005 and declined to 2001 levels by the end of the study. The rate of obesity dropped in Hispanic and Asian boys after 2005, but hadn't dropped back to 2001 levels by 2008. There was no increase in the prevalence of obesity in black boys, except in the severely obese category, which peaked in 2007. The rates in American Indian boys peaked in 2007, but declined only in the above 95th percentile group.

The rate in the over 99th percentile group didn't change for girls and changed little over the study period for boys.

"Research on health disparities is going to be very important in figuring out how we need to tailor our interventions to best meet the needs of different races and cultures," said Carolyn Landis, a psychologist and associate professor of pediatrics at Rainbow Babies and Children's Hospital in Cleveland, Ohio.

"The messages were originally developed for middle-class Caucasian populations," noted Landis, who added that the same messages won't necessarily work for all populations. For example, she said, in some areas, it's difficult to regularly find affordable fresh produce, and in some areas, it's not safe for kids to exercise outside. And that's where a tailored message might help, she said. Instead of telling parents to send their kids outside to play, suggest dancing around the house for an hour, she said.

Sleep can play a role in a child's weight, Landis said. Young children should get 10 to 11 hours of sleep; school-aged kids need 10 hours; and teens need at least nine hours, she said. Without enough sleep, it may be hard to be active or to make good food choices.

More information

The U.S. Centers for Disease Control and Prevention has advice on preventing childhood obesity for parents, teachers and school administrators.