All I can tell you is eat the right kinds of foods in the right amounts, drink lots of water and exercise everyday. Also when you eat a meal and you feel just right not too full or not full enough, stop eating. lol I know it's difficult but you can do it! Have fun doing it too. Ask your parents if they want to go for a walk with you that way the walk isn't so hard on you. When I walk alone I tend to walk a short distance because I don't have something distracting from getting tired. When you walk with someone you talk and talk lol and you don't really notice how far you have actually gone. lol well i wish you the best of luck! and remember don't over do it!