The glycemic index measures how fast the human body converts the carbohydrates in foods to glucose, according to WebMD. The lower a food's GI number, the less it affects blood glucose levels. For example, pumpernickel bread, beans and sweet potatoes are good foods for diabetic meal planning because they have glycemic index numbers of 55 or below, explains the American Diabetes Association. However, white bread, cornflakes and russet potatoes have glycemic index numbers of 70 or higher.
People use the glycemic index to plan meals by choosing low or medium GI foods as an alternative to high GI foods, notes the American Diabetes Association. They also combine high GI foods with low GI foods to create a more balanced meal.
More highly processed and cooked foods are typically higher on the glycemic index than less-processed foods, states the American Diabetes Association. For example, fruit juice has a higher GI value than whole fruit, soft-cooked pasta has a higher GI value than pasta cooked al dente style, and mashed potatoes have a higher GI value than baked potatoes. Ripening increases GI value, while adding fat or fiber to a dish typically decreases GI value. Meats and fats do not have a glycemic index value because, by definition, only foods containing carbohydrates are ranked in the glycemic index.