The index doesn't merely reflect whether the carbohydrates in a food are simple or complex. Many factors come into play, including the amount of fiber and fat in the food, how refined the ingredients are, and whether the food was cooked. Table sugar and honey are high on the glycemic index. But so are raisins, corn, potatoes, carrots, watermelon, doughnuts, white bread, instant rice, and most breakfast cereals. Apples, peaches, and ice cream, as well as most beans, grapefruit, and peanuts, are low on the index.
Pasta is in the middle.
The glycemic index has little practical use, however. Potatoes may be high on the index, but when eaten as part of a meal, they have much less of an effect on blood sugar. Even people predisposed to diabetes, or with the disease, can eat these foods in moderation. Carbohydrates, especially sugars, are the leading cause of obesity. It doesn't matter where those calories come from, as far as weight is concerned.