All carbohydrates break down into sugar for the body to use–but some do it slower than others!
Dr. David J. Jenkins and his colleagues at the University of Toronto were interested in finding which foods worked best for diabetics and in 1980, they coined the term Glycemic Index (GI). The GI is a comparative ranking of carbohydrates measuring the rate of release and the effects it has on blood sugar levels.
The GI scale is from 0 to 100. Foods with a high number such as white bread or a baked potato is digested and absorbed into the blood stream, having a resulting quicker rise in the insulin levels. Conversely, foods with a low-GI number like most fruits or pasta are released slower into the blood stream and affect insulin levels less severely.
Much has been made in the mainstream media about good and bad carbs, with low-GI being defined as good and high-GI as bad–especially with regard to weight loss. The GI scale does seem to have some effect on weight loss but does not live up to all the “hype” used for marketing purposes to sell a particular diet or product.
However, the GI scale is something to consider in the overall nutrition plan for diabetics. Two studies from the Harvard School of Public Health found that a “diet low in cereal fiber and rich in high-glycemic-index foods… more than doubled the risk of type 2 diabetes…” due to prolonged higher insulin levels triggered by the high-GI foods.
See this 2min 58 second video for a good explanation of the GI.