Great news, if true:

Federal health authorities on Tuesday reported a 43 percent drop in the obesity rate among 2- to 5-year-old children over the past decade, the first broad decline in an epidemic that often leads to lifelong struggles with weight and higher risks for cancer, heart disease and stroke.

The drop emerged from a major federal health survey that experts say is the gold standard for evidence on what Americans weigh. The trend came as a welcome surprise to researchers. New evidence has shown that obesity takes hold young: Children who are overweight or obese at 3 to 5 years old are five times as likely to be overweight or obese as adults.

I say “if true” because when it comes to government numbers, you have to look at them skeptically. We know that BMI is a pretty bad measure — have they improved it? Are we seeing fewer obese children, or simply better measurements? Are state and local governments fudging the numbers to get more aid? Are kids eating healthier and getting more exercise?

I hope it’s the last one, but the story never makes it clear.