I've heard a lot about this recently and a lot of what I've heard has pricked my BS radar, you know the thing, people saying that this that and the other is bad for you and but not explaining why, and by why I mean the science behind it.
So having read a bit around it, I wanted to see if my understanding is correct:
Carbs turn into glucose in the blood which is then absorbed as glycogen into liver and muscle cells to use as energy.
Glucose stimulates the release of insulin to manage that process, hence we talk about the 'glycemic index' of food.
Insulin regulates/promotes the storage of fat as well as inhibits the use of fat as an energy source.
Relatively higher levels of insulin in the blood thereby promote the storage of fat/inhibit its use as energy, so high GI foods can have a proportionally higher effect on net fat storage as a result.
If you're trying to lose or regulate weight, anything that results in a relatively higher insulin load will make that harder to manage.
GI is only part of the story; a better measure of this outcome is the Insulin Index which directly measures the proportional effect of a given food on the release of insulin into the blood stream.
How well does this summarise the situation?