The Glycemic Index is a numerical scale used to measure how quickly foods raise blood sugar levels. It ranges from 0 to 100, with pure glucose assigned a value of 100. Foods with a high GI (70 and above) are rapidly digested and absorbed, leading to a swift increase in blood sugar levels. On the other hand, foods with a low glycemic index (GI) of 55 and below are absorbed more slowly, resulting in a gradual rise in blood sugar.