The Better Question is Why Are Italians So Darned Healthy?
Of course, one of the main reasons for Italians staying so healthy is the way they eat. There is the Mediterranean diet itself, fish, fresh vegetables, fruit and the use of olive oil in cooking. Meats in Italy are not eaten in large quantities as in the U.S. and the amount of fat in the meats they prefer is also less. Meat is eaten as a separate course in smaller quantities, if at all. Lean pork is popular.
Even pasta and pizza are eaten differently in Italy. Italians eat simple pizzas with healthier toppings--not overloaded like American pizzas. Pasta is not served in large servings as in the States, either. As important for relieving stress in life, most families in Italy eat the family meal together--at the same time. Perhaps this promotes a feeling of well being and affords a sense of comfort to la famiglia.
In addition, the number of hills and steps the average Italian has to negotiate in their daily lives is much more than in the U.S. Most towns were built in an era of feudal warfare, causing them to be built on top of hills and cliffs for protection of their community. This means that most towns are very hilly and have thousands of steps and inclines. It amazed me whenever I saw octogenarians with canes going to the local alimentari to do their daily shopping. Exercise is something they get, whether they plan on it or not. During my three week Voyage though Italy, I lost 18 pounds, even though I felt like I was eating everything in sight... and gelato sometimes twice a day!
Oh, and one more thing. Stay away from faux Italian joints like Olive Tree. There is nothing on their menu that is anything like the healthy Mediterranean diet. There is no such thing as dipping bread in olive oil in Italy, and Italians don't automatically put a large bowl of bread or garlic knots (an American thing) on their tables.
Consider this old Italian saying... La salute prima di tutto! - Health is first of all!