Whole Health Source is one of the best health and nutrition blogs I've ever encountered. It's written in a totally accessible way by a young neurobiologist whose day job involves studying body fat regulation. He really knows his stuff and can explain complex biochemical processes in a way that doesn't make your eyes glaze over. When I stumbled across his blog I spent about three days reading my way through his entire archives! It's good stuff.
Boiled down to absolute bare bones, Stephan believes these three things are the most destructive elements of our modern diet: wheat, sugar/fructose, and omega-6 polyunsaturated fats (namely industrial vegetable oils). The quickest way to regain health is surely to eliminate these nasties from your diet.