The glycemic index is a ranking of carbohydrate containing foods. Foods are ranked according to their immediate effect on blood sugar levels. The higher a f ood raises blood sugar, the higher its glycemic index. Scientists published the first index in 1981 when they were researching diet therapy for diabetes. This first list contained 51 foods, and the list has continued to expand, with the most recent official list containing 750 foods. Fruits, grains, dairy products, some vegetables, pastas, and sugary desserts all contain carbohydrates, but have a wide range of glycemic indices. Meats, fats and some vegetables have none or very small amounts of carbohydrates and thus the glycemic index of these foods is low or close to zero.