Glycemic Index Definition
The glycemic index of a food is a number. This numeric value indicates how fast the carbohydrates in that food are broken down into glucose compared to a reference value, usually the GI of glucose or white bread, which is another fast carbohydrate. Only foods with carbohydrates have a GI; fat and protein do not have a GI.
You cannot know the GI of a food without looking it up, but you can make a good guess about which foods might have a higher or lower GI than other foods. Here are some general patterns.
Fiber is a type of carbohydrate, but your body cannot digest it, and fiber tends to lower the GI.
Processes such as cooking, mashing, and juicing tend to raise the GI.
Less processed foods, such as whole grains, tend to be lower-GI than more processed foods, such as refined grains like white bread and pasta.
Glycemic Load Definition
The GI of a food considers how fast the carbs in the food break down, but it fails to consider another important factor: how many carbs there are. To see intuitively why the amount of carbs is important, compare cooked carrots, with a high GI of 70, to peanut M&Ms, with a moderate GI of 47. Based on that information alone, you would think that the candy is a better choice.
However, when you consider theamountof carbs in each food, you get a more accurate picture. The glycemic load, or GL, multiples the GI by the amount of carbs in the food. The GL carrots is only 21, while the GL of a 2-ounce package of M&Ms is 110!
Glycemic Index Calculator
The GI of many foods have been determined through experiments to see what the effect of that food is on people’s blood glucose levels. You can find the GI of these foods and estimates of the GI of other foods using a GI calculator.