The glycemic index 'points' are only going to show you the effect foods will have on your blood sugar level... It will also show you how fast certain foods break down in your body and thus which foods are going to make you feel fuller longer.
Those points are in no way related to how much you should be consuming in a day to lose weight.
If you want to figure out how much to consume to lose weight, here's the deal:
Your body requires a certain amount of calories to maintain it's current
weight (body weight in lbs x 15)...so if you were 150 pounds, that would be
150x15 = 2,250 calories/day.
To lose 1 pound you need to be in a deficit of 3,500 calories. So if
you ate 500 calories less than this 2,250 each day (1,750 cals/day) you would lose 1 pound each week.
Now you could also couple that with 1 hour of cardio each day (500 calories burned/h on average) if you wanted to burn another 1 pound a week.
Of course to lose more, eat fewer calories or exercise more.
You can find more info on how to do that here.
