How long would you have to starve yourself for amenorrhea to take affect?

NOTE this is a hypothetical question and I am not in any way shape or form considering it. Just a medical question.

THanks.

Amenorrhea sets in when a woman's body fat drops below a certain percentage of her total body weight.

I did a search of several websites, but none said exactly how low the body fat percentage had to be. My guess is that it differs from woman to woman, and also depends on whether or not the woman is physically active and eats a healthy diet.

Some people argue that amenorrhea may not be unhealthy if it is caused by exercising. The increased muscle tone and blood flow to the pelvis that occur with a high fitness level may contribute to reabsorption of the menses, so hyper fit non-mentruating women may still be ovulating. Many elite athletes experience amenorrhea while training for important events. So do many ballet dancers, though I wouldn't necessarily hold them up as healthy examples.

Other women miss their periods due to stress, no starvation required. I tend of think of amenorrhea as the body's way of saying it's focused on something that's not compatible with fertility, either extreme physical training, extreme stress, or extreme lack of health. Hypothetically, if you create one of those conditions you'll interrupt your menses.

I hope this helps.