New York City measured children in kindergarten through eighth grade from 2007 to 2011 and reported the number of white obese children dropped 12.5 percent, while the number of obese black children dropped 1.9 percent, The New York Times reported.
The trend was repeated in big cities such as Los Angeles and smaller places such as Anchorage, Alaska, and Kearney, Neb., and even the state of Mississippi -- for many years ranked the fattest state in the nation.
However, Gary D. Foster, director of the Center for Obesity Research and Education at Temple University in Philadelphia, said these results were mainly among white children, but Philadelphia saw big drops in minority children.
Obesity among 120,000 public school students measured from 2006 to 2010 declined by 8 percent among black boys and by 7 percent among Hispanic girls, compared with a 0.8 percent decline for white girls and a 6.8 percent decline for white boys.
"The needle is actually moving," Foster told The Times.
Foster said he first noticed the change while conducting a study of middle school students that showed children part of a control group that did not take part in anti-obesity measures had a weight drop of nearly 4 percent, compared with 5.5 percent who participated in some weight control efforts.
Although several places are reporting children losing weight, researchers said they were not sure why students were losing weight, but it could be that the anti-obesity efforts to remove soda machines from schools, increase exercise opportunities, providing healthier school breakfasts and lunches, advertising campaigns and even the efforts of Michelle Obama might have begun to have an impact. However, many scientists have said they doubt anti-obesity programs actually work.