Does not compute

An article in today's AP news feed claims that 1 in 5 four year-olds are obese. Sure, obesity is a problem in our populace and it's no surprise that this is reflect in our children.

However, the definition they're using is suspect:

Children were considered obese if their body-mass index, a height-weight ratio, was in the 95th percentile or higher based on government BMI growth charts.

If they're using the 95th percentile, then only 1 in 20 (5%) of children are obese by definition.

What they really meant: "95th percentile or higher based on historical government BMI growth charts." In other words, a category which used to constitute 5% of four year-olds now represents 20% of them. Or, heck, quit with the political correctness and just set a number: obesity in four year-olds is defined as a BMI or 18 kg/m² or higher. Save the percentiles for justifying how you decided upon using 18 as the magic number.