body fat percentage question

I am 5'3". Average body type.  I recently lost a lot of weight. My body fat % is 8 and my nutritionest said it is very unhealthy to be that body fat percentage.  I stopped getting my period 4 months ago, and I am binging and malnourished.  She wants to see my body fat percent be at 18%.  When my bodyfat percent was 18 i was 125lbs and fairly heavy.  I'm 100lbs right now.  I know I have to be around 105/110 lbs to be at a better weight ((says doctors and nutritionests))

My question is:  I know girls who are skinnier then me, who have less actual body fat on them but can still be healthy and get their period.  Why can't I get it now that i finally lost all the weight. Why is my body fat percentage so crucial?.  I was just wondering.

So can someone thinner then me have a normal body fat percentage of 18% but still be thinner?  Will it be possible to get my body fat percentage higher but not actually be FATTER?

You can build muscle mass which will probably allow you to get away with a somewhat smaller bf %. 

You have to accept that 8% is too low, and that 5'3" and 125 lbs isn't as bad as you think it is. 

i was actually rather heavy at that weight.  But I know that 110 will be fine for me.  I'm 99lbs according to 1 scale and 103 according to another.  I binge almost every single night, and I have trouble gaining weight. I'm going to a doctor tomorrow to get tested for celiac disease.  Well thanks for the advice.

8% is waaay too low of a body fat %.  Congrats on realizing that you need to gain!  Basically, everyone's body is different and not all people are intended to be stick-thin.  Differing amounts of naturally-occuring hormones accounts for this difference.  At such a low weight, your body doesn't produce enough hormones to sustain your health or allow you to reproduce because it believes you are starving. 

I was always a really thin girl, but when I was 13, and for about 2 years (though I believe full mental recovery isnt' quite done) I became anorexic and lost a ton of weight, going from about 5'4" and 107 to 88 pounds.  I had to gain, obviously, to get my period back, which I typically do at about 108 or so.  But I know people who have set points significantly higher if they weren't always naturally thin.  In fact, I am about 111 or so now and about 5'4" and I'm still reallllly irregular. 

If you have any more questions, I would be happy to help!

Good nutrition is a factor in menstruation, not just body weight. I have lost my period at certain weights in the past on starvation diets, but am still menstruating at a lower weight now, because I'm getting enough of each nutrient. The periods stop not just from low weight but also from inadequate intake/nutrition.

18% is not actually "normal" although it's within a healthy range (14-19% is lean/athletic, 20-25% is still medically good, over 25% is unnecessary). You'd still be quite a bit leaner than average.

Some people who are naturally very thin don't actually have low body fat percentages. I know a woman who's taller and thinner than me, and seems very healthy, but she has almost no muscle definition.

That's very interesting information to know jinasolo.  I thought it was all about what weight your body is normally used to.  I'm always been a little bit on the heavy side throughout my whole life.  I find it unfair and frusterating to realize that I might not be able to be more lean because of loss of period (which clearly isn't healthy).  Do you know how long it takes for a malnourished woman to get nourished again if she eats the right foods each day?  My nails are brittle and my hair is dry and I feel I can be more healthier but my nutritious foods I'm intaking daily don't seem to be "working".