How do I get my dog to stay out of stuff?

When we are gone our 2yr. old golden ret. stays inside. And while we are gone he gets into our groceries on the shelf and pulls them out, tears them up, and eats it. Today when we got home he had pulled out and ate 2 1/2 packs of cookies, a bag of cheetos and a bag of potatoes. I don't know why he is doing this because I leave him food and water in his bowls. What can I do to stop him from doing this?