Kris
You are only 15. You're body is still growing and maturing. Don't diet too much or you will cheat your body out of necessary nutrient. the best bet is excersize. You can try walking/jogging for about 30 minutes a day 3 days a week. Then sit ups and maybe lift some little weights for your arms to firm up. But try to avoid starving yourself. If you excersize you can eat practically whatever you want. Good Luck