[condensr]

What MJM said is so right on. Its one of the more difficult things: eating different foods often and trying to understand how much insulin those foods will need, as well as how fast the foods absorb. There's just so many variables, its crazy. For instance, if you take the exact same meal side by side, but change the amount of fat in one of the plates, even though the fat itself may not directly affect your glucose, it'll change how much of the carbs are available in the food and how long it takes them to turn in to glucose.

So the IOB factor is only one part in determining a correction: you also have to consider food-on-board too. Like MJM said, the GI is important here.