In this Tuesday, Nov. 1, 2011 photo, first lady Michelle Obama sings and dances to exercises with staff, parents and children as she visits the Royal
In this Tuesday, Nov. 1, 2011 photo, first lady Michelle Obama sings and dances to exercises with staff, parents and children as she visits the Royal Castle Child Development Center, as part of the "Lets Move!" initiative in New Orleans, La. In 18 states, there were at least slight drops in obesity for low-income preschoolers, health officials said Tuesday, Aug. 6, 2013. (AP Photo/Gerald Herbert) (Gerald Herbert/)

After decades of rising, obesity rates among low-income U.S. preschoolers declined broadly from 2008 to 2011, according to a federal report released Tuesday that offered the first glimpse of good news for children considered among the most vulnerable to the disease's health risks.

While other, smaller studies have cited drops among school-age children, the data released by the Centers for Disease Control and Prevention (CDC) represent by far the largest and most comprehensive report of declining obesity rates in poor children, officials said.

Nineteen states and U.S. territories had a lower percentage of obese children aged 2 to 4, according to the report.

Officials said the decline was most likely attributed to three broad trends. More fresh fruit and vegetables instead of sugar-laden juices are among the healthier foods recently mandated in federally funded maternal- and child-nutrition programs. An increase in breast-feeding, which some research associates with lower risk of obesity, and greater public awareness of health and physical fitness programs are also making a difference.

Childhood obesity remains an epidemic that can lead to high blood pressure as well as respiratory and joint problems. As a result, experts have turned to a variety of measures to instill healthy eating and fitness habits at an early age, particularly among low-income youngsters.

"It's a bright spot for our nation's young kids, but the fight is far from over," said CDC Director Thomas Frieden. "We've seen isolated reports in the past with encouraging news, but this is the first report to show many states with declining rates of obesity."

The drops are small. But taken together, the data show the possibility that the country may have reached a tipping point, Frieden said. Instead of years of steady increases or no change, there is now a "true decline in many places around the United States," he said.

One in eight preschoolers in the United States is obese, and the rate is higher for black and Hispanic children. Children are five times more likely to be overweight or obese as adults if they have weight problems between ages 3 and 5.

Some of the biggest declines were reported in Florida, Georgia, Missouri, New Jersey, South Dakota and the U.S. Virgin Islands, the data show, although no state achieved a drop of more than one percentage point. Rates in 20 states and Puerto Rico held steady, and rates in three states — Colorado, Tennessee and Pennsylvania — increased.

No information was available for 10 states, including Virginia, Oklahoma, Louisiana and Texas. The Lone Star state has a large population of low-income children and a significant childhood obesity problem. Those states either didn't collect data consistently, changed the way they collected it, or didn't participate in the annual nutritional monitoring survey of low-income children.

Even if all 10 of those states had higher rates, "we would still have more states going in the right direction than the other direction," Frieden said.

Researchers said the states where obesity rates fell have taken action to incorporate healthy eating and active living into children's lives.

In a statement, first lady Michelle Obama, who has championed her "Let's Move" initiative to elevate the issue of children's health and fitness, said the results announced Tuesday show the country is moving in the right direction.

A child is considered obese if his or her body mass index, calculated using weight and height, is at or above the 95th percentile for children of the same age and sex according to 2000 CDC growth charts.

The CDC's data come from measurements of the height and weight of 11.6 million low-income preschoolers in 40 states, the District of Columbia and two U.S. territories — the Virgin Islands and Puerto Rico. Most were enrolled in the federal Women, Infants and Children (WIC) program, which provides food vouchers and other services.

Frieden said an increase in the number of youngsters covered in the program could have affected the data. But even so, the drop in rates is widespread and consistent enough to show "real impact," he said.

Marlene Schwartz, director of the Rudd Center for Food Policy and Obesity at Yale University, said the 2009 changes in the WIC program likely played a large role in the progress.

The program was altered to encourage purchases of fresh fruit and vegetables instead of juice, as well as whole-grain products and lower-fat dairy foods.

"The changes in WIC were massive," said Schwartz, who studied how the changes led more grocery stores in low-income neighborhoods to stock healthier foods.

Small children don't eat that much. An extra soda, or two to three cups of juice instead of one, makes a big difference, she said.

"If you are giving them unhealthy foods that are displacing more healthy ones, they will be more sensitive to those dietary changes than an adult who weighs 200 pounds," she said.

Other experts also said the progress, while small, was real. But health problems associated with childhood obesity tend to show up when children are 10 to 14 years old, and those problems are still on the increase.

"We are not experiencing a decrease in the rates of liver disease or diabetes or sleep apnea," said Jeffrey Schwimmer, a pediatrics professor at the University of California at San Diego and director of a weight and wellness program at Rady Children's Hospital in San Diego. "We're still seeing greater numbers of children being diagnosed with those problems."