The Glycemic Index (GI) is a relative ranking of carbohydrate foods according to how they affect blood glucose levels. The lower the relative value, the slower the metabolism of the food, and thus the slower the food causes an increase in blood glucose.
Any rise in blood glucose, of course, affects insulin levels, a critical consideration for people who are diabetic or pre-diabetic.
However, attention to the GI is a good idea for everyone, because spikes in blood sugar due to what we eat can lead, over time, to ever-increasing proximity to a diabetic state.
So---it's not just about sugar!
Ultimately it's about how rapidly any food raises our level of blood sugar.
Find out more at https://www.gisymbol.com/about-glycemic-index/