The largest food group in a low-carb diet should be vegetables (excluding starchy ones like corn, potatoes and beets). Ideally, at least half of your dinner plate should be covered with vegetables. A good lunch would be a large salad with protein and dressing added. Even breakfast can have vegetables included, for example in an omelet or other egg dish.
Select a variety of colors of vegetables and fruits, as the phytonutrients and antioxidants are different in the different color groups. Also, since each food contains a different combination of nutrients, you are more apt to get all your needs met when you eat a variety of foods.