slate reports on a new study showing a link between body fat in girls and the early onset of puberty. puberty has dropped, on average, about 4 years in the past century. i’ve seen the current avg reported differently in different studies. i’ve seen as low as 10.5, and as high as 11.4 (as averages, that is). but that number has plummeted in the past 30 years. for a long time, studies were inconclusive as to the reason. some suggested it was a physiological response to cultural pressure to enter quasi-adulthood at younger and younger ages. others suggested it was a better diet (more rounded). others suggested it was preservatives in food. but, in the last few years, my observation (really, just my anecdotal observation) is that most studies seem to now be saying the reason is tied to how we eat, and, specifically, to all the junk we eat. there ARE trends to younger puberty in cultures that don’t eat the junk of western culture (and, especially, american culture); but the drop in those cultures doesn’t seem to be as extreme.
does anyone know of a comparative study, showing avg ages from a wide variety of cultures?
anyhow, here’s a quote from the slate article on the new study:
“New study: Now, some new research by Joyce Lee and Julie Lumeng of the University of Michigan and their colleagues offers some clarity. They studied about 350 girls of diverse socioeconomic and geographic origins, all born in 1991. The girls’ heaviness was estimated at 3 years of age and again at 4½ by calculating their body mass index percentile, an indirect measure of obesity, normal weight, or thinness. The girls were then tracked over time for evidence of the onset of puberty. As was expected from previous research, other factors like race, mother’s age of puberty onset, and mother’s education played a role in predicting when a girl would reach puberty. But none of these factors were nearly as important at predicting early puberty as a history of being overweight at age 3 or 4.”
(ht to anastasia)