The Glycemic Index measures the impact of carbohydrate containing foods on blood sugar levels. Foods with higher index values raise blood suger more rapidly than foods with lower glycemic index values do. Eating a lot of foods that rank high on the glycemic index will produce spikes in blood sugar that can lead over time to loss of sensitivity to insulin, the hormone needed to allow blood sugar to enter cells for use as fuels. Insulin resistance is associated with obesity, high blood pressure, elevated blood fats and an increased risk of type 2 diabetes. When planning meals, include as many low GI foods as possible. Exchange high GI breads and cereals for lower GI alternatives. Use the GI and GL food tables provided in this Guide to plan your meals and make optimal GI choices.