A Swedish medical study found boys were found to hit puberty at younger ages than ever before.
From 1947 to 1996, for each subsequent decade, boys were getting taller about one and a half months earlier—from 14 to 13—that's from high school to junior high.
"There is a role that increasing weight, increasing BMI, contributes to earlier onset of puberty," said Kelsey Seybold's Dr. Pam Sanders. "There are a number of chemical exposures in the environment that are thought to possibly disrupt hormones and trigger earlier puberty in both boys and girls."
She said parents and pediatricians need to be prepared to talk to boys earlier about puberty and body changes--like around 9 and 10 years old, and younger for girls.