Girls are starting puberty at younger ages and these findings are causing physicians concern, The Week reports. Increasingly more girls are starting puberty before age 10. Based on changing diets, obesity trends and exercise levels, I'm not surprised. Some girls enter puberty younger because they have central precocious puberty. Medscape says girls with CPP start hormonal changes younger than the normal ages of 9 to 15. My mother started puberty at age 8. Read more at Girls Hitting Puberty Younger Isn't Surprising