Literary texts, archaeological records, classic iconography are all sources which allow us to declare that the Mediterranean diet, to which today we make reference to, has a strong and close relationship with various aspects of the Greek-roman culinary tradition and, in particular, of the Magna Graecia, that is the territory attributed now to the actual southern Italy and colonized by the Greeks starting from the eighth century BC. To appreciate the ancient origin of the Mediterranean diet let us trace down, in this chapter, Greeks and Romans dietary habits. This brief survey of the ancient Greeks and Romans eating habits shows how the different uses of food of those days have been passed on and refined over the centuries in coherence with the dietary models described in the following pages and subject of study by Ancel Keys in early 1900. An abundant supply of cereals, legumes and vegetables, intake of olive oil and wine, the presence of fish and in limited quantities of meat and cheese are the corner stones of the Mediterranean food diet.