Watch the documentaries "Forks Over Knives" and "Game Changers" as a couple of good places to start. Read the book The China Study. You can't eat a S.A.D diet (Standard American Diet) and be healthy. It's impossible. And working-out can only get you so far, and won't reverse heart disease (everyone that eats an American Diet has heart disease). Drugs can't either - only diet can. Diet is king, exercise is queen. But it takes an entire re-examination of what you've grown up with... most people can't do it and just want another drug or fad diet which will change nothing. If you can make the jump it will be life altering.
