What makes foods have different GI levels?
Foods that have the same amounts of carbohydrates can have very different GI levels depending on the variety (such as long-grain and short-grain rice), how much they are processed, how ripe they are and how big their particles are. For example, diced potatoes may have a higher GI than a whole potato. Fiber will make a difference too. A sweet potato will have a lower GI than a white potato because the fiber content in a sweet potato is higher. Also, the amount of fat consumed in a meal can slow down glycemic response.
