Good, unexpected news on the childhood obesity front, at long last.

From The New York Times:

After decades of rising childhood obesity rates, several American cities are reporting their first declines.

The trend has emerged in big cities like New York and Los Angeles, as well as smaller places like Anchorage, Alaska, and Kearney, Neb. The state of Mississippi has also registered a drop, but only among white students. …

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The drops are small, just 5 percent here in Philadelphia and 3 percent in Los Angeles. But experts say they are significant because they offer the first indication that the obesity epidemic, one of the nation’s most intractable health problems, may actually be reversing course.

Part of the decline is due to children no longer eating massive chunks of cheese

Part of the decline is likely due to children no longer eating massive chunks of cheese.

Before you start printing up flyers crediting your co-op and/or chicken coop, know this: It’s not entirely clear why the drop is happening.

The first dips — noted in a September report by the Robert Wood Johnson Foundation — were so surprising that some researchers did not believe them. …

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Researchers say they are not sure what is behind the declines. They may be an early sign of a national shift that is visible only in cities that routinely measure the height and weight of schoolchildren. The decline in Los Angeles, for instance, was for fifth, seventh and ninth graders — the grades that are measured each year — between 2005 and 2010. Nor is it clear whether the drops have more to do with fewer obese children entering school or currently enrolled children losing weight. But researchers note that declines occurred in cities that have had obesity reduction policies in place for a number of years.

As the Times story notes, the link between obesity and economic class is maintained even in this decline.

Obesity affects poor children disproportionately. Twenty percent of low-income children are obese, compared with about 12 percent of children from more affluent families, according to the C.D.C. Among girls, race is also an important factor. About 25 percent of black girls are obese, compared with 15 percent of white girls.

Some experts note that the current declines, concentrated among higher income, mostly white populations, are still not benefiting many minority children. For example, when New York City measured children in kindergarten through eighth grade from 2007 to 2011, the number of white children who were obese dropped by 12.5 percent, while the number of obese black children dropped by 1.9 percent.

But Philadelphia, which has the biggest share of residents living in poverty of the nation’s 10 largest cities, stands out because its decline was most pronounced among minorities.

While the random geography of the decline could prove an asset in identifying common threads, the sheer breadth of things that have been tried may make finding successes complicated. The larger cities, like New York and Philadelphia, have developed a number of programs intended to fight the problem. Like Philadelphia’s robust program to provide fresh food in low-income communities — is that part of the city’s broader success?

If nothing else, the news should be embraced by the Army, which is suffering from a spike in discharges of soldiers who are out of shape. Maybe this is the frame the food movement has needed all along: government investment in local farming to ensure military dominance. Tanks ploughing up empty lots. That sort of thing.

It’s not certain that the decline will continue; the data is still being analyzed. But one thing is for certain: It’s only a matter of time before Monsanto or Yum! Brands puts out an advertisement taking some credit for the drop. I think there are still slots available during the Super Bowl.