" Not surprisingly, refined carbohydrates cause a surge in insulin levels. What was astounding was that dietary proteins could cause a similar surge. The glycemic index does not consider protein or fats at all because they do not raise glucose, and that approach essentially ignores the fattening effects of two out of the three major macronutrients. Insulin can increase independently of blood sugar. "

― Jason Fung , The Obesity Code: Unlocking the Secrets of Weight Loss