I was a chubby kid who weighed 120 lbs at age 10. I was only 5 feet tall, and very athletic. After a LIFETIME of trying to lose weight, I finally found ketogenic eating, and do not consume sugar (even fruit). At 56, I am now 110 pounds without cravings. Sugar is a terrible substance. No amount of willpower, sports, or good intentions will overcome its ill effects if you are sensitive to it (most of us are). Sports and exercise will not overcome a bad diet. Your granddaughter needs to get some education. I know fat camp can scar kids, but maybe some time away where she only has wholesome, sugar-free foods. In the meantime, every piece of positive feedback you give to your granddaughter will help. If you see her eating the right foods (no snacks or sugar), tell her she is a champ! Positive reinforcement can work wonders.