Isn't this coming round to the old, simple system of 'exchanges'? I know this looks more accurate, but exchages were very easy to use. David's Response Derek Paice, who developed the substance glycemic index, sent me this reply to Martin’s comment: Unfortunately, the exchange method does not directly address A1C control. The glycemic index teaches that for those with type 2 diabetes, the carb source affects its impact on blood glucose. The exchange system, as I understand it, does not make that distinction. One exchange is about 15 grams of carbs, whatever the source. The SGI (substance glycemic index) defines glycemic effects based on food weight, not carbs. Further, for those with some mathematical capability the SGI can be personalized to predict their A1C. For people making negligible insulin, such as those with type 1 diabetes, a simple simulation model shows that total insulin dose is independent of glycemic index. Here’s where the carb is a carb is a carb rule applies. However, the AUC (area under the curve) is predicted to be lower for lower GI foods, a result supported by observations of some who have had type 1 diabetes for many years.