That is a complete myth. GI is taken way out of proportion. Please show me one scientific study showing high GI carbs lead to more fat gain than eating low GI carbs.
Not to even mention when you eat a meal it usually has protein or fat with it. Protein, fats, or fiber all reduce the GI of the entire meal.
Here watch a video-
Low GI Myth
If you want actual scientific studies I will post those up as well.
edit: Sry if that came off as a little aggressive. Its just diet myths and the "no steroid burns fat only diet and exercise do" myth are two things that really grind my gears.