Hi, Feisty and KenpoDoc gave you good advice, I'll third that. My daughter was about your height at 15 always working on exercising more to lose. That, I kept telling her doesn't work and it didn't. (she was in TKD-lst Dan now) Finally she stopped drinking pop, eating cookies, candy, ice cream, chips, crackers. (never ate fast food) Instead she ate smaller portions of other foods, fruit, yogurt occasionally for snacks, etc. and then she really did lose weight (think she was really doing it for her boyfriend but...).
Eat whole grain carbs, like oat cereal, occasional scrambled eggs, cut back on fats. Good fats-olive oil, canola oil, occasional peanut butter in celery, walnuts, skim milk, low fat cheese-remember small portions. Meat- chicken, fish, low fat beef-sauteed, grilled, baked, grilled, not fried. Potatoes- not so much, rice, coucous, macaroni products-not so much, wheat bread, multivitamin.
Salads for lunch are great. If your high school offers them and they have meat, maybe some cheese, good veggies, these are great. You do need some wheat crackers, or yogurt with this though for carbs. Use low cal dressing. Eat broccoli, green beans, zucchini, summer squash, tomatoes, green, and colored peppers, mushrooms, onions, some corn, some carrots, cucumbers,celery, eggplant. Ask your mom, if she likes to cook. Otherwise, alot of these can be eaten raw in a low cal dip.
A small treat is ok but only once a day. But limit your calories, fat and sugar. Read the labels. For that matter, sugar in food causes fat. Like Jello with marshmallows in it. A lot of prepared foods (packaged) have hidden sugars. French fries are the worst, high carb and fried in bad oils. Not any of this is set in stone, its just to give you a guideline. Discuss this with your Mom and she can help you.
PS. I think a good amount of water like 8 cups a day are important. But I use big glasses 12-16 oz so one glass is a fourth of the water I need. So 8 oz is better unless you have just exercised. I drink tons. Its also good to drink a cup of water a hour before class too, especially in this weather.
Eating right is a lifestyle not a diet to lose weight but if you are careful your body will shed pounds. Choose well. TW