This is being looked at partly as overweight driving early puberty. Underweight could just as easily drive late puberty--a decrease in late puberties would contribute to a "worsening" here.

Similar to the obesity epidemic, when you look at it from a BMI perspective. Take an overweight person, and add ten pounds of lean mass to them--do this enough times, and you've turned an epidemic of people being "overweight" into an epidemic of being "obese."