Don't call her an idiot! teach her!

I think idiot is just a little too harsh. But I understand the surprise of your child not knowing something you think they should know. For example, my 12-year-old is just now starting Sex Ed. I tried to teach him since kindergarten so that he would know the truth and while he vaguely understands how the sperm gets to the egg and what the outer body-parts are called, I had to explain that its normal to get hair on your scrotum. And that is the technical name for ball sac

You should've written "I raised an idiot". Young girls are bombarded with sexualized images of feminine beauty that are impossible to reach, and without the guidance of a parent, this will greatly impact their self-esteem and health. Don't give your daughter barbies, don't let her watch horrible MTV shows about plastic-looking spoiled rich kids, and don't make comments about her weight and what she eats. Provide her with healthy ideas with what real women look like, and don't let her obsess about her looks at such a young age. Get in there and do some parenting, OP.

She is part your genes

I don't think she's an idiot. That's pretty harsh as a parent. She's 13; all young kids think stupid things sometimes. She'll grow out of it.

Well first tell her to not believe everything you read or hear and then teach her to read labels for nutritional value. Good luck.

Your daughter's an idiot? Who raised her?

She's 13 so it's more of how you're raising her. They learn by example at that age so who's the idiot

Why does your 13 yr old even think she should diet?

Sounds legit. Let her give it a try :-)