What foods help you lose weight?

I'm 13 and want a flat 6 pack! I'm not lazy I do a minimum of 20 hours of sport a week so it's not exercise I need to get my flat stomach. I've done research into what to eat but im quite cod used as some websites say something is good and some say it's bad! What do I eat and avoid for a flatter stomach?
What foods help you lose weight?
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