After several decades of rising childhood obesity rates, several cities are reporting their first declines.
The rates have dropped in both big cities, like New York and Los Angeles, and smaller cities, like Kearney, Nebraska and Anchorage, Alaska.
Mississippi, the fattest state in the country, also reported a decline but only among its white students.
“It’s been nothing but bad news for 30 years, so the fact that we have any good news is a big story,” said Dr. Thomas Farley, the New York City health commissioner. The city reported a 5.5 percent decline in the number of obese schoolchildren from 2007 to 2011.
In Philadelphia, the decline was five percent, and, in L.A., it was three percent. While the drops are small, experts say they are significant because they offer the first indication that the obesity epidemic may finally be reversing.
The first declines were noted in a September report by the Robert Wood Johnson Foundation. Researchers initially didn’t believe the numbers.
Deanna M. Hoelscher, a researcher at the University of Texas who recorded one of the earliest declines among mostly poor Hispanic fourth graders in the El Paso area, was uncertain about the dips.
“We reran the numbers a couple of times,” she said. “I kept saying, ‘Will you please check that again for me?’”
Researchers are unsure of why the rates of childhood obesity are dropping. It is unclear if the drops are due to fewer obese children entering school or to currently enrolled students losing weight. But researchers are noting that the declines are happening in cities that have already had obesity reduction policies in place.
Nationally, about 17 percent of children — or 12.5 million people — under the age of 20 are obese, according to the Centers for Disease Control and Prevention. The CDC defines childhood obesity as a body mass index at or above the 95th percentile for children of the same age and sex.
The childhood obesity rate has tripled since 1980 but has leveled off in recent years.
Low-income children are disproportionately affected by obesity. Twenty percent of low-income children are obese compared to 12 percent of children from affluent families. Race is also a major factor, with 25 percent of black girls being obese compared to 15 percent of white girls.
In New York, which measured children in kindergarten through eighth grade from 2007 to 2011, the number of obese white children dropped by 12.5 percent. The number of obese black children dropped only 1.9 percent.
In Philadelphia, obesity among 120,000 public school students from 2006 to 2010 dropped by eight percent among black boys and seven percent among Hispanic girls. The decline was 0.8 percent for white girls and 6.8 percent for white boys.
“The needle is actually moving,” said Gary D. Foster, director of the Center for Obesity Research and Education at Temple University.