Oregon has the nation’s lowest rate of hefty kids, according to a new government study, which found big gaps between regions and ballooning obesity rates in many states from 2003 to 2007.

More than 16 percent of American children ages 10 to 17 years were not just overweight, but obese, in 2007. That’s a 10 percent rise from 2003. Mississippi topped the nation with more than a fifth of its kids obese.

Oregon was the star, with the lowest rate of obesity — defined as body mass index in the 95th percentile or above — at just under 10 percent. And Oregon was the only state whose childhood obesity fell significantly from 2003 to 2007.

Even the best states fell short. The federal Healthy People 2010 initiative set a childhood obesity goal of 5 percent. Only Wyoming girls came close to that, according to the study appearing in May’s Archives of Pediatrics and Adolescent Medicine.

“You’ve got such wide differences at the geographic level, which means there is potential to further reduce obesity,” said lead author Gopal Singh, an epidemiologist with the U.S. Health Resources and Services Administration.

What works? It’s unclear how much states can overcome the effects of poverty, race and family history — all of which have complex links to obesity.

Black and Hispanic young people in the study were twice as likely as whites to be overweight or obese, even when the researchers took into account other risk factors like inactivity and poverty.

Oregon is 90 percent white. It also has a high rate of breast-feeding, and some research suggests that protects against obesity.

Oregon law sets nutrition standards in schools and requires chain restaurants to provide nutritional information on request. Those steps, taken recently, wouldn’t have shown up in the new study’s results, but may reflect Oregon’s inherent interest in health.

The figures for this analysis came from a representative telephone survey of parents who gave information about their children. Figures for about 47,000 children were analyzed for 2003 and about 44,000 children for 2007. That’s not as accurate as a government survey that weighs and measures children. Data from that suggest childhood obesity rates nationwide may be starting to stabilize.

In a separate paper based on the same data, Singh found that a child living in a neighborhood with unsafe surroundings, poor housing and no access to sidewalks, parks and recreation centers had 20 to 60 percent higher odds of being obese or overweight.

Experts blame the rise in childhood obesity on fast food, neighborhoods without sidewalks, television, video games, schools neglecting physical education and a host of other societal changes, said Dr. Joe Thompson, director of the Robert Wood Johnson Foundation Center to Prevent Childhood Obesity.

Now, lawmakers must move the obesity numbers in the right direction to save future medical costs, if for no other reason, Thompson said.

Right now, one of most known medicines for reducing obesity is Meridia (Sibutramine).

Researchers led by Jeanne Van Cleave, a doctor at Massachusetts General Hospital for Children in Boston, looked at the prevalence of conditions that lasted a year or longer in three groups of children, starting with a first cohort of more than 2,000 kids in 1988.

That group was tracked for six years, after which a second group was studied between 1994-2000 and finally a third group from 2000- 2006.

Mothers of the children were asked whether their kids had any “physical, emotional or mental condition that prevented him or her from attending school regularly, doing regular school work or doing usual childhood activities, or that required frequent attention or treatment from a doctor or other health professional.”

The information gathered was classified into one of four categories of chronic condition: asthma, behavior or learning disorders, obesity and other physical conditions.

“We found that prevalence of a chronic condition at any point during the study period was very high and increased over time,” the authors of the study, published in the Journal of the American Medical Association, said.

“Many factors may have contributed, including environmental changes, which may affect rates of chronic respiratory conditions and obesity,” and greater access to health care for children during the study period, which would have boosted diagnoses of childhood chronic conditions, the study says.

Reports of all chronic conditions, including the much-talked-about childhood obesity, rose from just under 13 percent at the end of the six-year follow-up for the first group of children to 26.6 percent in 2006, the study shows.

The obesity rate rose from 13.3 percent at the end of the first study group, in 1994, to nearly 16 percent at the end of the third cohort in 2006.

In the third and last group the researchers looked at, 51.5 percent of eight- to 14-year-olds “at one point in the six-year study period reported a chronic condition compared with 27.8 percent in cohort one,” the study says.

But unlike chronic conditions in adults, the childhood conditions were not necessarily long-lasting, the study said.

More than half of children who showed asthma-like wheezing before they were four years old had stopped having breathing difficulties by age six, and children with certain behavior disorders overcame them within a year.

The study also confirms what other recent research has shown: that obesity in the United States has reached a plateau.

There were fewer new cases of obese children reported in the third group of children — between 2000-2006 — than in the second group, a finding “consistent with previous reports of flattening childhood obesity rates in recent years,” the study says.