The glycemic Index is a measurement of the way the blood sugar responds two hours after a certain food is ingested in comparison to the way it responds two hours after an equivalent amount of pure glucose is ingested. The lower a food's glycemic index is, the less is the body's glycemic response to that food. By eating foods with lower glycemic indexes, you can maintain a more stable blood-sugar level. For the glycemic indexes of some common foods. The glycemic index is important for two primary reasons-it indicates the metabolic consequences that different foods can have, and it helps when foods with certain glycemic indexes need to be consumed at specific times. For example, it is better to consume foods with low glycemic indexes for meals and snacks, since these foods help maintain the proper blood-sugar level and ensure a sustained energy supply. Conversely, during workouts and competitions, it is better to eat foods with high glycmic indexes because these foods help spare glycogen in the body and supply quick energy to exercising muscles.