It's really simple. You are what you eat.
No really, that kid on the playground teasing you 25 years ago, he was right.
If you put shit in, you are gonna get shit out. Thats the honest truth. And it seems like common sense, but as one of my all time favorite quotes goes, "Common sense is not too common."
But if you want to know the secret to looking better, feeling better, performing better, its really very simple. Put quality in and get quality out. You wouldn't expect your car to run very well if you filled the tank with cheap, half booze, dirty gasoline would you? Then why do so many people think that they can fill their bodies with cheap booze and "dirty" (read: processed) food and still look/feel/move well?
I've said it before and I'll say it again, eat real food instead of stuff out of a box. Avoid processed and refined sugar. In fact, avoid sugar in any form as much as possible. Get protein and fat, fruits and vegetables, and do your best to not drink you dinner, and you will be ahead of the game.