The glycemic index (GI) is a system of ranking foods that contain equal amounts of carbohydrates according to how much they raise blood-glucose levels. (The lower the GI number, the less the food boosts your blood sugar and the more diabetic-diet-friendly it is.) The GI is somewhat confusing and even a little controversial. But, in general, it does lead you to healthy foods. For example, vegetables, whole grains, beans and high-fiber foods tend to fall lower on the glycemic scale, while processed and refined foods and sweets are higher up.