Our weight affects our hormone levels. Being overweight, while still able to have periods, can cause fertility problems because the hormone levels are too high- (extra estrogen comes from the fat cells.) Being undeweight can disrupt the hormones to the point that periods stop altogether; it causes the body to produce too little estrogen. I don't believe the pill can be lessened by anorexia. Rather, I think that the normal estrogen is so low that even the pill cannot cause menstruation to occur.