So, for one of my classes, we measured body fat in a few different ways. Each had a different result, but we were told that the electrical impedance was the most accurate. My body fat percentage was measured at 13 on the electrical impedance scale. Based of the stuff we were looking at, 13 was considered underweight, but I feel like I'm healthy. They were saying that with being underweight, comes problems with menstruation, but I have no problem with menstruation. I'm not sure what else they said, but I know that gymnasts often are not healthy and you can see it in their hair, but my hair is healthy. I also don't watch my weight. I seem to stay between 105 and 110 ish, no matter what I do. Although, last winter I was at or above 110 and this winter I am 105. Does having small breast size change all of this? For example, someone with naturally large breasts might be underweight if she makes it down to 13% body fat, but someone with naturally small breasts might not be? What are your thoughts on an electrical impedance scale measuring my body fat at 13%?