Furthermore, the GI does not consider protein or fats at all because it measures only the effect of carbohydrate containing foods. (idmprogram.com)
When researchers looked at carbohydrate containing foods, there is a very close correlation between the GI and the amount of insulin released (Insulin Index — II). (idmprogram.com)
Lastly, Protein rich foods release insulin too, much more in some cases compared with carbohydrate containing food. (nutritionfacts.org)