"Their health had almost nothing to do with what they were eating" -- It's good to be young, isn't it? As you get older, the effects of what you put into your body become more immediate, even when you exercise.
In it, there's a great heuristic for walking out of your local supermarket carrying food (as opposed to processed "edible foodlike substances"): shop near the edges.
Still, most diet advice is useless. Here's the only advice you need: "Eat food. Not too much. Mostly plants." Quoted from a NYT article: http://www.nytimes.com/2007/01/28/magazine/28nutritionism.t....