Marc and Dan are twins who like the same activities, and foods. At a recent doctor's appointment, Dan was told that he has type 2 diabetes. He has been feeling good and has not noticed any changes in his health. He does not understand why he has diabetes but this brother does not and why he has not had any noticeable symptoms. How would you explain this to him? Describe what the glycemic index is and how this is very important in developing a nutritional diet.