U.S. News offers this clarification in its latest letters section:

“How to Win the Weight Battle” [September 10] stated that 17 percent of kids are now obese, which means they’re at or above the 95th percentile for weight in relation to height.

The reason that a greater percentage of kids now fall into the “top 5 percent” category is that the standard measurement charts that define obesity were created using data from the 1960s and ’70s, when kids weighed less than they do now.

While it’s entirely possible that kids weigh more than they did 40 years ago because more kids are obese, it’s also possible that a higher standard of living has played a role in making more kids taller, stronger, and (consequently) heavier.

I wonder how the figures might change if researchers factored in changes in kids’ heights during the same interval. Even better would be a comparison of measurements of body fat in the 1960s and 1970s to the same measurements today.