Body Mass Index is crap! Yes change the equation and you can get any statistic. Keep in mind that since the change to BMI, the President of the United States is considered overweight. Back in the day, he never would be considered overweight. Ridiculous, but good for those in the faux BMI business I suppose.
This is so much BS, I drive thru Mexico every day and see these kids walking around the block. I drive thru one of the last bastions of America in California and see 30 girls or 30 boys running 3 miles and loving it.
In Reseda, Mexico where I live you wont find kids riding bicycles, riding skateboards, or bouncing a basketball. You wont see a motor home unless it is lived in. you wont see a boat or jetski. Mexicans just plain dont do physical activities. When we talk about childhood obesity, we are talking about Mexicans.
If childhood obesity is hitting a plateau perhaps it is because the number of homeschoolers is growing and improving the average.