What you have to remember with sugar is that it's a lot of calories for very little volume. There is no other reason sugar makes you fat other than the fact you can eat a lot of it without being full. The insulin response can be avoided being eating enough fiber and fat with foods. The GI of foods is tested on a fasted individual, so once other food is added you tend to see it become irrelevant. A classic diabetes diet is all carbs and no fiber. My sister being a prime example. Eat around 10-15g of fiber per 1000calories you eat. If anyone else want's advice on the gym and nutrition feel free to hit me up, this is my
forte.