I know I’m certainly not the first person to write about childhood obesity, and I won’t be the last. The world doesn’t need another guy ranting about the consequences of poor eating habits and how these choices are sending our nation off the deep end. So rather than examine the risks of being an overweight child or adolescent, I’d like to look at how America’s youth earns the title of “obese” in the first place.

According to the Centers for Disease Control and Prevention, obesity is determined by the child’s or adolescent’s — ages 2-19 — BMI in relation to their gender and specific age. The result is then plotted on the CDC’s growth charts and receives a percentile ranking. Anyone above 85 percent is overweight, and anyone above 95 percent is obese.

If this definition follows its own logic, it means that exactly 5 percent of American youth will be obese at all times, regardless of what the average happens to be. It would mean that even if the entire nation was in ideal shape — an impossible notion, I know — there would still be 5 percent of children and teens that peak over that obesity line.

However, the statistics show that this isn’t the case. The CDC also says that a 2008 study “indicated that an estimated 16.9 percent of children and adolescents aged 2-19 years are obese.”

Now, I know what you’re thinking: “Wait … how are 16.9 percent of America’s youth fitting into an area of 5 percent?” While that’s a legitimate question, it’s not exactly how the calculation works. The growth charts display percentage curves that “illustrate the distribution of selected body measurements in U.S. children,” the CDC explains — measurements that aren’t necessarily the same as the ones that determine BMI. Then the child’s BMI is compared to these percentage curves.

But don’t give the system too much credit — this doesn’t mean that it makes total sense. The problem lies in the relationship between the growth charts and the BMI calculators, which is hard to see because each method works on its own. However, once you mix them together and use percentage as the unit for two entirely different systems of measurement, there’s bound to be some confusion. Even the CDC warns, “Growth charts are not intended to be used as a sole diagnostic instrument,” and mashing BMI values against it doesn’t seem to be any better. The only way to really learn where these calculations come from is to study the statistics for the growth charts, which are currently available in a handy 203-page PDF from the CDC’s website. Good luck.

So how can we, as a nation, try and stop childhood obesity when the methods used to diagnose it are so tangled? As long as parents still don’t realize that they have control over what their kids eat, and the Cookie Monster warning that cookies are only “a sometimes food” isn’t doing the trick, there doesn’t seem to be much we can do. I suggest that a good place to start is creating a new system to define obesity that is more absolute. Right now, one body measurement compared to a percentage ranking based on other body measurements’ percentage in a statistical distribution of an ever-changing average is simply not cutting it.