While the right age for a girl to hit puberty and experience first menstruation was supposed to be 13 years and above these days girls experience periods much early than the said age. However this is not with all girls though. Early puberty hits girls who experience certain physiological and emotional changes that induce hormonal imbalances and trigger early puberty. Another contributing factor towards early puberty in girls is childhood obesity. Excess fat especially abdominal fat in the body alters the levels of different hormones like estrogen insulin and leptin and leads to early puberty or early periods in girls.