How can my mom think I'm anorexic?

I am 30 pounds overweight!!! I eat 3 meals every day and my mom is threatening to take me to the doctors! She says I need to eat AT LEAST 1000 calories per day but if I'm eating all my meals then 500 calories isn't that bad. It's just that I eat low calorie food items like salads and chicken and I work out. We've been fighting so much I don't know what else I can say to her.
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I am 5'5" and weigh 174lbs
How can my mom think I'm anorexic?
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