'Why would it help? In youth, the theory is that physical activity itself lowers estrogen levels. Studies of teen athletes show that very intense exercise can delay onset of menstrual cycles'

Or, perhaps, exercising at 12 means you're more likely to continue exercising and therefore be healthy instead of a big fatty. Obesity contributes to breast cancer.

Let's look at the simple things we know before we postulate new things about delayed menarche or decreased estrogen hey?