There's no one "Mediterranean" diet. Common Mediterranean dietary pattern has these characteristics:
high consumption of fruits, vegetables, bread and other cereals, potatoes, beans, nuts and seeds
olive oil is an important monounsaturated fat source
dairy products, fish and poultry are consumed in low to moderate amounts, and little red meat is eaten
eggs are consumed zero to four times a week
wine is consumed in low to moderate amounts
Mediterranean-style diets are often close to our dietary recommendations, but they don’t follow them exactly. In general, the diets of Mediterranean peoples contain a relatively high percentage of calories from fat. This is thought to contribute to the increasing obesity in these countries, which is becoming a concern.
More than half the fat calories in a Mediterranean diet come from monounsaturated fats (mainly from olive oil). Monounsaturated fat doesn't raise blood cholesterol levels the way saturated fat does.