There's yet another reason to worry about the obesity epidemic among America's kids: Extra weight may be sending U.S. girls into puberty earlier than ever.
Researchers have found that girls with higher body mass index, a ratio of height and weight, may start developing breasts more than a year before their thinner friends—perhaps as early as second grade.
The change is spawning a whole new market of child-sized sanitary pads—decorated with hearts and stars—and deodorants aimed at 8- to 10-year-olds, according to a new study and an editorial published Monday in the journal Pediatrics.
"The girls who are obese are clearly maturing earlier," said Dr. Frank Biro, a pediatrics professor at Cincinnati Children's Hospital Medical Center. "BMI is, we found, the biggest single factor for the onset of puberty."
In addition, white girls are maturing about four months earlier than in a landmark 1997 study that shocked parents with the news that their daughters who played with My Little Pony could be entering puberty.
Biro's team followed more than 1,200 girls ages 6 to 8 in three cities—San Francisco, Cincinnati and New York—from 2004 to 2011, carefully documenting their BMI and their maturation process.
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On average, girls with BMIs below the 50th percentile started developing breasts at about age 10, while those in higher categories—the 85th and 95th percentiles—began developing as early as age 8.5.
Why is this happening? Although they're not certain, scientists including Biro say that extra weight might trigger the body to believe it has enough energy and other resources to kick off puberty—even when the child in question is only 8.