Quote Originally Posted by Dianyla View Post
I've always read that about 15% body fat is required to support regular ovulation/menstruation.
Just about every place I've looked says something different. One site even proposed that normal menstruation would stop if a woman were to fall under 22%, which I think is probably not the case for most women. Given the differences in various people I would say how much fat you need to function is likely pretty variable too.

In any case just some rapid weight loss, even if its not down to below your lower limits can temporarily interrupt your cycle as can stress.