The percentage of children with obesity and severe obesity has nearly quadrupled over the last 50 years.

This week, the Centers for Disease Control and Prevention expanded its body mass index (BMI) charts to better accommodate the trend.

Released in 2000, the BMI for age growth charts are widely used to track childhood growth and spot obesity.

But they’re based on data from 40-60 years ago, when rates of severe obesity — defined as 120% of the 95th BMI percentile — hovered closer to 1% than 6%.

So the CDC has extended those charts beyond the 97th percentile to better track growth and offer a visual aid for discussing obesity and treatment options with families.

Today, 4.5 million kids ages 2-19 have severe obesity and face greater risk of developing conditions like type II diabetes, high blood pressure and depression.