And that hormone leptin travels in the bloodstream across the blood brain barrier and goes to the hypothalamus and can trigger the onset of puberty by activating the neurons that release gonadotropin releasing hormone . So many people believe that one of the reasons that puberty is happening earlier and earlier in females is because of the accumulation of more body fat at younger ages than was observed 30 or 40 certainly 100 years ago . Now , I can already imagine a number of people are thinking , oh , this must re relate to the obesity crisis .
Well , that's an easy one to answer over the last 100 years or so . The onset of puberty has been occurring much earlier with each passing decade . It's really an incredible set of statistics .
These are ongoing collections of data , but just to give you a sense to how the data are falling out in a couple of different countries just to give you a a flavor . But for those of you listening and for those of you watching , the essence of all of these findings is that puberty is happening much , much earlier with each passing decade . So for instance , in the United States , around 1900 or 1903 , the average age of men or the onset of puberty in females was about 14 years old .
However , if we look at , for instance , the data from Norway , which dates back uh quite far , they have excellent record keeping to 1850 . What we see is that the average age of the onset of female puberty in 1850 in Norway was 17 years old , whereas in 1970 it's 13 years old . So this is a dramatic acceleration of the onset of puberty and you see a similar trend in other countries as well .
So there will be exceptions , there's a distribution of data today . Still there will be uh young females who will undergo puberty at age 11 or 10 or maybe even nine and others who will undergo puberty at age 1314 , maybe even 16 or 17 . However , if we look at , for instance , the data from Norway , which dates back uh quite far , they have excellent record keeping to 1850 .
