Glycemic Index
Via Nadnut who decided to deck up as a hot nerdy teacher:
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.