New research shows that the childhood obesity epidemic is the primary reason that young girls are developing breasts at an earlier and earlier age.  

For the study, published in the journal Pediatrics, researchers evaluated the development of 1,200 young girls in San Francisco, New York, and Cincinnati. At the onset of the study in 2004, the girls were between the ages of six and eight.  They were examined periodically over the next seven years.

Researchers found that the average age of thelarche - a big word for the onset of breast development - was earlier than previously recorded for white girls at 9.7 years old.  Black girls were found to experience breast development around 8.8 years, Hispanic girls at 9.3 years, and Asian girls at 9.7 years.  They also found that a high body mass index, or BMI, was a strong indicator of early puberty.

What is unclear is whether or not early breast development will also lead to an earlier onset of menstruation.  But they do know that girls that develop breasts earlier struggle with issues such as lower self esteem and depression.  

"Girls with earlier maturation are at risk for lower self-esteem and higher rates of depression," wrote Dr. Frank Biro an author of the study and a pediatrician at Cincinnati Children's Hospital.  "They are more likely to be influenced by older peers and more deviant peers, and initiate intercourse, substance abuse other norm-breaking behaviors at younger ages," he added.

The study also noted that early maturation has been linked to an increased risk of breast, ovarian and endometrial cancer.

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