In his introductory sentences to In Defense of Food: An Eater's Manifesto, Michael Pollan has captured the essence of sound nutritional advice. Here is a link to his book jacket and a PDF of his intro. He gets it, and he writes brilliantly about a difficult subject: what's so bad about the American way of eating, and how to change it. Yet somehow he manages to stay chatty and engaging as he writes about depressing subjects such as the 32-billion dollar "Food Marketing Machine" and the shifting sands of nutritional science (or the reason my patients are so confused).
I believe women need more than this to get back on track when they are 35+ and having trouble figuring out what to eat without developing middle-age spread, but it's the finest and most eloquent place to begin.
See you at the farmer's market.