Glycemic Index

There seems to be a growing tide of media discussion about the glycemic index and the glycemic load, particularly regarding people who are overweight. Reducing the amount of sugar you ingest, plus eating in moderation and a little exercise is a well respected plan for losing and controlling your body weight with But, is it all that simple? What’s the big deal about the two glycemic numbers?

Glycemic Index

The glycemic numbers are very important for patients diagnosed with diabetes or in a prediabetic condition. Simply stated, the glycemic index (GI) is a measure of the comparison between foods containing carbohydrates and sugar (glucose) and blood glucose levels. Studies have measured the blood glucose values of a fixed quantity, 100 grams, of carbohydrate foods against a similar quantity of glucose. Determining the GI is not an exact science per se. The number can vary depending on the study source. But, through years, the GI of many foods have been somewhat standardized and accepted.

Glucose is the standard, set at 100. The tested carbohydrate foods fall into three groups based on the GI results; low, medium and high. GI below 50 is considered low, 50 to 70 medium, and 70 to 100 is high. The glycemic index is just a scale so one can identify the relative blood glucose effect of certain foods. Obviously, those concerned about lowering blood glucose should choose foods with a low GI. The caution here is the glycemic index is a relative scale and does not take into consideration the quantity of food eaten. Advice suggested is to use the GI to balance your sugar intake while being mindful of quantities eaten.

Also, be aware that the glycemic index of a particular food can change depending on ripeness, processing and cooking. The classic example is a banana. An unripe banana may have a GI of 42, while a ripe one may have 52. And, as the banana becomes over-ripe the number increases.

For the diabetic and prediabetic patient, controlling blood glucose levels is imperative. Moreover, knowing how fast, how high and how long blood glucose change with carbohydrate foods is just as important.

Glycemic Load

Glycemic load (GL) is a measure of rise in blood glucose based on the glycemic index and portion of the carbohydrate food eaten. Many believe that the glycemic load factor is a better guide in controlling blood glucose levels because it addresses the quantity of a food. The higher the GL the faster blood glucose levels will spike, and then, for most, fall off. This, in turn, puts stress on the insulin response. Whereas, a lower GL food will rise slower and maintain a lower blood glucose level over a longer period of time. A GL of less than 10 is considered low, 11-19 medium, and above 20 high. The formula to determine GL is the total carbohydrates in grams times the glycemic index (GI) divided by 100. TC(g) * GI/100.

The glycemic load depends on the portion of the food. Many GI lists will use 100 grams for portion size just for numeric uniformity. Other lists will compute the GL based on the “normal” portion size which, of course, is not always 100 grams.

If you want to compute the GL of a product using the supplied nutrition label be sure to deduct the “Dietary fiber” quantity from the total carbohydrates listed. The mean GI for a popular candy shown below is 55. The GL 18.7.