Liz is right, there is no formula for restriction, as everyone is different.
For me I cannot tolerate more than a quarter of a slice of bread, 1 tablespoon of rice or a few pasta shells. But I only use these to test my level of restriction. I do not eat them on any regular basis.
But I would like not to be able to have them at all, so I am off for another fill.
This one I hope to get there.