To answer your question, I think a brief statement on what the glycemic index is would be useful. Glycemic Index (GI) is a measure of the effects that carbohydrates have on our blood glucose (sugar) levels. In actual fact the GI is a scale between 0 and 100. Carbohydrates that are broken down quickly in our gut cause our blood glucose levels to rise quickly after eating and have a high GI. Alternatively carbohydrates that are broken down more slowly have a low GI and relase glucose more gradually. Examples of the two are as follows:
Low GI - Porridge, Apple and Sweet Potato.
High GI - Jasmine rice, Cornflake and Watermelon.
Here is a good website which lists foods in terms of their GI - http://www.gilisting.com/
Generally simple carbohydrates have a higher GI because they are more easily broken down by our gut (due to their simplicity).