How to convince your parents to let あなた become a vegetarian?

I talked to them about 2 years 前 about me wanting to become vegetarian, and they gave me permission and even bought me soy ミルク and tofu. The first week was fine and I felt good about myself but the 秒 week I got sick and they sent me ホーム from school. I know it wasn't the tofu または the soy, it was that I had bulimia (laxatives got me sick quite often) but my parents thought it was the vegetarian diet I had had for that week.

So they forbid me to become a vegetarian and I tried to explain to them that it wasn't because of the diet but because of my loss weight diet. Anyways they told me I could only become a vegetarian when I turned 18 and によって that time I was 13, now I'm 15 but I don't want to eat nay もっと見る meat, but every time I bring the subject my parents won't listen.

Any advice?