Add one more reason to the long list of reasons to support Michelle Obama's initiative to prevent childhood obesity: it will help reverse the trend of girls starting puberty at younger and younger ages. A new study shows a rapid trending downwards of the average age of girls beginning puberty, and the escalating rates of childhood obesity are being eyeballed as the likely culprit.
There's some suggestion that environmental estrogens could play a role, but that's unproven, while it's well-known that body fat does produce hormones that can kick start puberty. Granted, it's not an either/or situation---it's possible that a combination of environmental influences and increased body fat play a role. Nonetheless, the relationship between weight and puberty isn't, from what I understand at least, particularly controversial. It makes evolutionary sense that the body would start puberty once enough fat has accumulated that the body can support a pregnancy, and of course we know that severe anorexics often stop menstruating once they drop below a certain amount of body fat. As long as everything's working properly, the biology of all this is pretty neat. I recall from Natalie Angier's book Woman: An Intimate Geography the general rule that menstruation begins after a girl reaches a certain weight, usually around 100 pounds. If you're not overweight, this usually happens right before you teenage years, but as kids get fatter younger, we're seeing puberty start to happen at much younger ages, at least in girls. In this study, 10% of white girls, 23% of black girls, and 15% of Hispanic girls age 7 had enough breast tissue to have started puberty.
What to make of all this? It's true---and most women can attest to this reality---that once your hips and breasts start to come in, harassment from men follows shortly thereafter, and this can be traumatic for very young girls. I bristle at the notion that the solution for this is preventing early puberty instead of fighting a culture that turns a blind eye to men harassing women on the street. Instead of manipulating girls' bodies, why not manipulate the culture to accept girls as they are?
However, men harassing young women isn't the only consideration on the table. There's an problem when the age of sexual maturation predates emotional maturation, and that gap increasing isn't something to wave off. Adolescence is hard enough without extending the number of years you have to suffer it into elementary school. And, as the researchers pointed out, the earlier you go through puberty the higher your chances of suffering from various cancers later in life. As preventing too much weight gain in childhood is something theoretically in the realm of control, it's a place to focus efforts.
Photograph of Michelle Obama in her White House vegetable garden by Paul J. Richards/AFP.