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Why Are Girls Reaching Puberty So Young?

We're not sure what it was like in your elementary school, but in ours, it was way uncool to sport boobs before hitting middle school.

But times sure are changing for our girls, as a new study points out. Researchers recently looked into just why so many girls are entering puberty at younger and younger ages than ever before. The biggest factor that turned up? Childhood obesity. (Surprise, surprise.)

The study looked at more than 1,200 girls between 6 and 8 years old in the San Francisco area, the Cincinnati area and New York City, examining them multiple times between 2004 and 2011. (Entering puberty was considered to be the age each girls' breasts started to develop.)

Black girls were found to start puberty at the youngest age of all—8.8 years old. This news isn't exactly groundbreaking, considering other similar studies have turned up the same stat. But for other minorities, the average age of entering puberty has clearly been lowered: for Hispanic girls it was 9.3 years, and for Asian girls, it was 9.7.

White girls were also found to enter puberty around 9.7 years old—but this is a whole three to four months younger than they did in 1997, according to another study. And that's even younger than the average age researchers recorded back in the 1960s.

Remember when you could give a ballpark guess as to when you'd get your period, based in when all the other ladies in your family did? Well tracing back the family tree doesn't seem like an accurate indicator now; the study found that ethnicity and genetics have less to do with the onset of puberty and more to do with a kid's Body Mass Index (BMI).

"The influence of BMI on the age of puberty is now greater than the impact of race and ethnicity," study researcher Dr. Frank Biro said. Biro is also a professor of pediatrics at Cincinnati Children's Hospital in Ohio.

Speaking to LiveScience, Biro said: "These girls were born and raised in the midst of an obesity epidemic. [And] this is yet another impact of obesity epidemic in this country."

We can't pin it all on the obesity problem, though. Lifestyle changes play a part, too. Things like getting in less daily activity, dealing with more stress, and eating less fruits and vegetables also have a significant impact.

“Each individual girl is exposed to multiple factors in today’s environment, many not present decades ago, that may potentially influence her pubertal onset,” said Marcia Herman-Giddens, a researcher at the University of North Carolina, Chapel Hill.

But the real worry for experts is just what this early maturation is doing to our kids in the long run, especially when some research suggests early puberty is linked to type 2 diabetes and high blood pressure.

As for now, though, more research is needed to know for sure.

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