Kids entered fifth grade more obese every year, but they did not gain more weight and their overall fitness improved as they moved to higher grades.

"We accomplished a significant first step and that is to slow obesity," said Dr. William Bommer, a cardiologist at the University of California, Davis, who worked on the study. "But we importantly were not able to reverse it."

The researchers, whose report is published in the American Heart Journal, recorded the fitness gains after California mandated exercise time and healthful eating in public schools across the state in 2005.

While the findings suggest the prevention programs may be helping, they can't prove the programs caused the health improvements.

Obesity is associated with high blood pressure, diabetes and other ailments in children and adults. About 17 percent of children and teens in the United States are obese, according to the Centers for Disease Control and Prevention.

In response to rising obesity trends, California required public schools to provide an average of 20 minutes of physical exercise per day for kids in kindergarten through fifth grade, and 40 minutes for grades six to 12. Schools also had to increase the quality and quantity of health education and could no longer serve high-fat, high-sugar foods and drinks.

Bommer's team tracked data from more than six million students in fifth, seventh and ninth grade from 2003 to 2008, after these measures took effect.

At each grade level, the students took fitness tests which included body mass index (BMI) measurements, endurance runs, push-ups and shoulder stretches. The researchers analyzed those test records for changes in obesity and fitness.

They found some encouraging signs. Though the number of obese kids continued to increase (two percent more children were overweight or obese in 2008 than in 2003), the rate of increase seemed to be slowing.

Obesity rates rose an average of 0.3 percent per year during the study, compared with about 0.8 to 1.7 percent per year in previous national studies.

Students showed small improvements in body fat and weight as they progressed from fifth to seventh to ninth grade. They also got better -- or at least did not get worse -- in physical fitness areas such as abdominal strength, upper body strength and flexibility.

One particular finding defied researchers' expectations: more students entered fifth grade obese every year, however they didn't gain further excess weight between fifth and ninth grades.

"We thought that probably what we'd find was the entrance class was about the same (every year) and kids were gaining weight during the school years," Bommer explained.

Nor did the fifth-graders lose the weight as they progressed through the grade levels. Indeed, Bommer's team attributes the overall rise in rates of obesity and overweight seen among all students during the study period mainly to the rise among the incoming generations of fifth graders.

Further research is needed to determine whether this early obesity develops before kids get to kindergarten or during elementary years, Bommer told Reuters Health, as well as where future interventions could make a difference.

"If you become obese as a student or adolescent, it's very difficult to reverse that obesity when you're an adult," he added.

Dr. Maura Frank, a professor of clinical pediatrics at Weill Cornell Medical College in New York, described the California programs as a model for other states.

"When we work with individual families or schools, if we don't have the support of public policy, nothing can be done," said Frank, who wasn't involved in the study. "It's a prerequisite for change on a population level."

The findings on growing obesity rates among fifth graders are equally important, she told Reuters Health.

"It highlights the need to start with interventions earlier," she said. SOURCE: American Heart Journal, February 2012.

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