Hey girl!!
I've actually heard that dairy is beneficial in weight loss! It's the calcium. The fact that you're 15 years old makes it so very important that you get enough of that calcium for your bone strength too. You might benefit from talking to a dietitian. Even talking to your rheumatologist about this would be helpful.
I've tried diets, but they don't work. For me, it's the prednisone that is making me fat! I don't overeat, and I eat good wholesome foods. It's the stupid prednisone that is such a hard thing to lose weight on. Are you taking prednisone?
Maybe some others can give both of us more encouragement on a good diet plan!
Ginny