i was wondering why, even though my weight is relatively normal that my period has been missing for 9 months? I am 5'8 and lost about 25 pounds and am now 130 lb. This gives me a bmi of almost 20, but i am still have no period. I calculated my body fat percentage to be about 17.5%, which, from what I have been reading, is too low to have a period. How can my bmi be in a totally healthy range but my body fat percentage so low? Do i need to gain fat and lose muscle? And what fat% is necessary to maintain a normal period?
Your cycle is not influenced alone by body weight and muscle. You seem to be at a healthy weight.
There are plenty of other factors that may be affecting your cycle. Have you seen a gynecologist about your hormone levels?
For instance your body fat percentage is very low, which is common for very athletic women. Yet more directly it is not uncommon for women who are athletic to have high testosterone present in their body, which can cause the absence of menstruation.
The problem now would not be how much fat to muscle you have but your hormonal irregularities.
I would recommend seeing your doctor for a lab work up.