Your weight is based on how you respond to your appetite, not on how much you exercise. Fat and protein are low GI. So are most whole grains and basmati rice. It's the white flour and sugar (the primary non naturally occuring foods in our diet) that have the highest GI. Fructose (fruit sugar) is the only low GI sugar.
and for those who don't know, high GI foods increase your appetite by causing a spike in insulin levels which makes you hungry after the food you eat has been broken down.