Focus on things that come from the earth, not a factory. The best advice is, when shopping at the grocery store, stay along the outside walls where you find fruits, vegetables, beans and lean sources of meat. All of these occur naturally. This helps keep those processed foods and sugar-packed snacks, all of which will kill your metabolism, out of the cart. Also, leave the white potatoes behind. This vegetable contains an awful lot of starch that your body converts to sugar almost immediately with little work.