I strongly disagree with this:
> Pretty much any diet which is free of anything should be avoided.
For the couple of years, I've been trying various elimination diets so that I can see what effects particular foods and food groups have on me. Even if I had ended up with exactly the same diet, it would have been worth doing, as I learned a lot about my body and my relationship with food.
As it happens, though, I want to keep some pretty big changes. After doing my 3rd Whole30 [1], a paleo-esque 30-day elimination diet, I'm just finishing a week where I returned to eating refined carbohydrates. My conclusion: as much as I enjoy those foods, they make me feel terrible. My mood and energy were much less even. They put big demands on my self control, and make me prone to binging. I sleep less well. Starting tomorrow, I'm going to spend a few months without refined carbohydrates again (sugar, flour, juices). I'll probably drop dairy again too.
I don't know that I'd recommend my particular choices for anybody else, but I strongly encourage curious people to experiment with elimination diets. If nothing else you get the sort of exercise in self-control that religious people get from Lent, which I think is valuable on its own. But I learned a ton along the way, and wish I had done this years ago.
[1] http://whole30.com/