The importance of Glycemic Index when counting calories?

[AthalaRanger]

The importance of the Glycemic Index when counting calories?

This has been bothering me for a while, and I thought I should ask.

For those who don't know what the Glycemic Index is (GI from now on), this is the definition provided by wikipedia:

The glycemic index (GI) provides a measure of how quickly blood sugar levels (I.e, levels of glucose in the blood) rise after eating a particular type of food. The effects that different foods have on blood sugar levels vary considerably. The glycemic index estimates how much each gram of available carbohydrate (Total carbohydrate minus fiber) in a food raises a person's blood glucose level following consumption of the food, relative to consumption of pure glucose. Glucose has a glycemic index of 100.

Some time ago (over 2 years), I read about this and I started to believe that foods like potatoes or bananas were the absolute worst things that I could eat while trying to lose weight.

Because of this, every time I tried to lose weight, I would to avoid most foods that could rise blood sugar quickly, resulting on a very limited diet. That was until I started counting calories.

My question is; does the GI of a food matter while trying to lose weight, assuming that the person is under his maintenance calories?

Some clarifications here;
a) The question is assuming that the person doesn't have a medical condition that requires an special attention to blood sugar levels.
b) The question is mainly about fruits and vegetables, which one could assume are bad because of their GI. (I.e: potatoes, bananas, pineapples, watermelons, etc)

If we consider carbohydrates such as bread, does it matter if a person consumes them, as long as he is on a caloric deficit?