The glycemic index is a method for ranking the impact of a carbohydrate-containing food on blood glucose in comparison to a reference food, such as glucose. A food with a high glycemic index raises blood glucose higher than a food with a low glycemic index.
Meat and fats don't have glycemic rankings because they don't have carbohydrate components. Non-starchy vegetables, dried beans, fruits and legumes have low glycemic index rankings. On the other hand, bread, corn cereal, white rice, processed foods and melons have high glycemic index rankings. The glycemic index ranking of a food is lower when fiber, fat and protein are present.