energy cannot be created or destroyed. when you spike insulin (i.e. energy), then you either USE it, or you STORE it. It doesnt just disappear. So eating a meal that is high in simple carbs can cause fat storage, which will be fat you just have to diet more to lose.
If you follow the rules, body composition will be optimal. You won't store any fat while you are in a deficit. Alan Aragon, one of the best nutritionists put it like this:
"Also note that I no longer give a damn about GI, it doesn't really make a difference one way or another. If you want high GI carbs pre and/or during training, go for it. As time has passed, GI has proven itself to be a worthless, irrelevant index."
read some books instead of just relying on wavelengths word...
there are a lot of books on how insulin affects fat gain (atkins, etc.)
one book i recommend for some thought is "nutrient timing" there is some useful info in this book to be gained.
I would recommend reading book by authors who actually rely on scientific studies and know how to interpret them. Atkins is not one of them.