GI = Glycemic Index. A low GI
diet is one in which the things you eat will not spike
blood sugar levels, but will work
to help stabilize them.
For instance, eating a piece of candy will spike your blood sugar rather quickly, whereas eating a carrot will not, because of the lower sugar/carb content. Regular pasta will spike your blood sugar more quickly than whole gain pasta because it takes longer to digest the whole grain, so it doesn't go straight to the blood.