Please help...I think my sister has an eating disorder

Hi I would like some advice...I think my sister Tasha is anorexic! She always says she fat and she is skinny she only eats 1 meal a day  and works out after eating it so she can burn the calories. She says she not hungry when she is...she tells me that she is so scared of becoming fat!! She says it gives her control! I found a
book she writes in and she writes about food she says she can't stop thinking about it and she only let's herself have 400 calories a day...she won't eat junk food anymore
I'm really worried about her...July 16th 2010 she weighed 120 and now she weighs 110 I know all this stuff because I have been watching her carfully and sometimes she tells me about it I also read her book she writes in...I'm just really worried about my big sister! My family is starting to notice her not eating...we all tell her that it is not health to stop eating and tell her to eat more she just says I eat ok I don't know what I should do? What do you think about this?

[Amber_T]

She is 15 turning 16 in 20 days her height is 5'4

[Zoelula]

I think you are right to be concerned. Have you tried talking to her and expressing your concern? If you do and she blows it off, I would suggest speaking to your parents. She is headed down a very dangerous road.