You should probably eat things that are good for you, like fruits, vegetables and protein, and not eat too much that is bad for you, like boxes full of ingredients. And don't worry about coffee and a little bit of alcohol.
The way those concepts are fleshed out in the story is pretty compelling: http://mobile.nytimes.com/2007/01/28/magazine/28nutritionism...
I think a safe intuition is lots of cookies and chips are probably bad for you, and mostly vegetables, fruits and protein are probably better for you.
Don't worry about the best diet, just try to be sensible.
What the hell does this mean?