I'm adding this as there have been questions on what the Glycemic Index and what it is and how it works.
The Glycemic index (also glycaemic index) or GI is a measure of the effects of carbohydrates on blood glucose levels. Carbohydrates that break down rapidly during digestion releasing glucose rapidly into the bloodstream have a high GI; carbohydrates that break down slowly, releasing glucose gradually into the bloodstream, have a low GI. For most people, foods with a low GI have significant health benefits. The concept was developed by Dr. David J. Jenkins and colleagues  in 1980–1981 at the University of Toronto in their research to find out which foods were best for people with diabetes.
A lower glycemic index suggests slower rates of digestion and absorption of the foods' carbohydrates and may also indicate greater extraction from the liver and periphery of the products of carbohydrate digestion. A lower glycemic response is often thought to equate to a lower insulin demand, better long-term blood glucose control and a reduction in blood lipids. The insulin index may therefore also be useful as it provides a direct measure of the insulin response to a food.
Here is one site that is good, if you go to Google there are others but I trust Medosa the most. There are two parts to eating according the Glycemic Index. The GI and the GL number. The GI is the number given the food in testing on the Glycemic Index and the GL is the Glycemic Load of the food per serving. GI should be 55 or less and GL should be 11 or less then you will be fine. You still have to watch portion sizes so you don't gain weight because regardless of the GI or GL or Carb a calorie is still a calorie but if you eat this way you can eat more!!! :)
This site might be a little easier to understand.
A list of common foods and their GI
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