We have long known that our kids are eating themselves into early graves. As it turns out, they may also be eating themselves into early puberty.
Girls are developing breasts and starting to menstruate earlier than in previous generations, studies have found. While a number of factors probably contribute to this change, among the biggest culprit is fat.
Young women with a higher body-mass index — the ratio between a person’s height and weight — are more likely than their slimmer sisters to enter puberty earlier, with some girls developing pubic hair as early as the age of 2.
“Among all the things we know and suspect might play a role in the onset of puberty, BMI is the major one that everyone agrees on and has a well-documented impact,” said Dr. Lawrence Kushi, principal investigator in the CYGNET Study, a large, federally funded epidemiologic project focused on understanding pubertal maturation in girls.
But this is where things get tricky. Fat not only causes the hormonal shifts seen in puberty, it is also a by-product of puberty — a time when every woman’s estrogen levels and metabolism change. Which means it’s not always easy to determine which came first, the fat or the development.
“It seems like a parallel sort of thing: Sexual maturation is kicking in the whole estrogen-metabolism pathway, so when that starts, part of what that also does is alters fat metabolism,” Kushi said. “More fat tissue also can help to increase the body’s level of estrogen. So, it’s probably both things happening in both directions.”
Still, 17% of children in this country are obese, triple the rate from a generation ago. Nutritionists advise parents to keep their young girls away from sugary drinks, make sure they get plenty of exercise (an hour a day is ideal) and eat their fruits and veggies.
Will that keep puberty at bay? It’s unclear, but it can’t hurt, said Dr. Frank Biro, professor of pediatrics at the University of Cincinnati.
Boys too seem to be entering puberty earlier. Unlike girls, however, data about weight’s effect on puberty in boys are conflicting.
Biro and Kushi are currently working on a study to determine the exact new median age of puberty’s onset, but suffice to say it’s much earlier than when you (or your sister or wife or girlfriend) remember it.
From 1920 to 1984, the average age a girl got her first period dropped from 13.3 to 12.6 for white girls and 12.1 for African-American girls, according to a 2007 study. Research published in Pediatrics in 2010 found that 10% of white girls and 23% of black girls in the US begin developing breasts by age 7.
And the drop in pubertal age appears to be increasing, with girls in this country entering puberty far earlier than they were even a decade ago, researchers said.
It’s a trend the feminine-hygiene market has noticed, designing products specifically targeted toward girls as young as 8. Kimberly-Clark, the makers of Kotex products, for instance, now market kid-size pads and tampons sold in boxes festooned with third-grade-friendly glitter and stars.
While market researchers and physicians ponder whether truncated childhoods are the “new normal,” many parents of girls who enter puberty early have sought out medical experts, alternative remedies and online support groups. And with good reason: Early puberty is associated with earlier sexual activity, as well as an increased risk of developing breast cancer later in life.
“We interact with kids the way they look. If a 10-year-old looks like she’s 14, she will be talked to and treated like she’s 14. She doesn’t have a sign on her that says she’s 10,” Biro said.
Though fat is thought to be the most significant factor in cases of early puberty, it’s likely not the only one. In a series of nationwide studies funded in part by the National Institutes of Health, researchers are examining environmental toxins and societal factors that could contribute to this phenomenon.
In particular, scientists are investigating the link between early-onset puberty and endocrine-disrupting chemicals found in everything from building materials to personal-care products. In a 2010 study, researchers found an association between early breast development and a high exposure to three classes of common chemical compounds — phenols, phthalates and phytoestrogens.
A third of the girls in that study were also overweight, and scientists caution that more research is needed to determine how significant a factor these chemicals are in hastening puberty, but it couldn’t hurt to limit a girl’s exposure to them, Biro said.
Look for personal-grooming products that are labeled “phthalates free,” for instance. And avoid microwaving food in plastic, including plastic wrap. The phthalates in plastic leech into food during heating.
Among the most surprising findings of the research so far is one by Julianna Deardorff, an assistant professor in the School of Public Health at University of California, Berkeley, who discovered girls in upper-income households without a biological father in the home were twice as likely to experience early-onset puberty.
Deardorff, who is also a clinical psychologist, said it is unclear why a father’s absence could make girls “grow up” so much faster. She theorizes that exposure to more artificial light from TVs or computers or contact with more chemicals from beauty products could play a part, but these are just theories.
Regardless, she said, parents are going to have to rethink how they contend with their really little women.
“Puberty is so sexualized in this country, so parents get a little panicky,” Deardorff said. “They’re still little girls. We should be explaining the changes that are happening instead of jumping to fears.”