For the first time in decades, a number of US cities are reporting a decline in childhood obesity rates—an unexpected shift that had researchers checking and re-checking their data. Big cities have seen dips: Between 2007 and 2011, the rate fell 5.5% in New York, 5% in Philadelphia, and 3% in Los Angeles. Smaller cities like Anchorage have also seen rates drop. "It’s been nothing but bad news for 30 years, so the fact that we have any good news is a big story," says New York's health commissioner.
In fact, it could herald a change in the obesity trend, the New York Times reports. But the reasons for the shift remain unclear. Scientists aren't sure Michelle Obama-style programs to fight obesity are effective, and researchers don't know if kids are losing weight or if fewer obese children are starting school, the Times notes. Still, with 17% of those under age 20 obese, cities like Philadelphia have made big pushes against the epidemic, ridding school cafeterias of deep fryers and removing sugary drinks from school vending machines. Now, "the needle is actually moving," says a researcher. (Read more childhood obesity stories.)