Hi, the insulin index Nutrita uses is a better predictor of the metabolic impact a food is likely to have because predictions based on blood sugar increases (GI) or the total carb load (GL) have many more false positive and false negative errors.
Nutrita's Insulin index has been extensively refined to minimize these errors.
The problems with GI and GL:
For example, 100g of carbs from a potatoe increases blood glucose less than 100g of carbs from potatoe flour. the Glycemic Load cannot distinguish that.
The Glycemic index looks at rises in blood sugar and suffers another problem, in that it can't tell you how much insulin it 'cost you' to maintain blood sugars. so you could be thinking "hey my blood sugars are normal this food is fine for me!" but in fact you're producing a tsunami of insulin to keep stable blood sugars. So the GI will miss prediabetes, basically.
Check out these podcasts and studies which go through the science papers demonstrating this https://www.breaknutrition.com/episode-8-starch-digestibilit... and https://www.breaknutrition.com/episode-7-processed-starches-...
