The so-called Mediterranean diet is claimed to be preventive with respect to diet-related degenerative diseases. It is suggested that the preventive effect especially with respect to diabetes might be the low glycemic index of this kind of diet. However, nutrients with a high GI are more frequently consumed in the Mediterranean diet than in other European countries. The major difference seems to be the higher amount of fiber and a higher intake of unsaturated fat together with a higher intake of fruits and vegetables. Based on recent studies from the nurses health and physicians health study, a diet which is similar to the Mediterranean diet, physical exercise and a BMI < 25 protects from the development of diabetes type 2.