If you ever have the opportunity to eat Italian food in Italy, don't go overboard with the tip. Italian waiters tend to be paid very well, and in most cases you'll be charged a fee called a coperta that covers your bread, table settings, and the like. Tips should be limited to a maximum of 10% (although of course the waiters would appreciate more!)
Low carb dining can be difficult in Italian restaurants, but it's not impossible. Avoid pasta, pizza, and bread, and zero in on meats, seafood, salads, and antipasto. Olive oil is also good, because it contains antioxidants and the kinds of fats you need to maintain good health.