You can probably do some simple monitoring with a blood glucose meter like diabetics use if you are really interested.
You'd track your blood sugar levels after eating a standardized carbohydrate meal. If you see a rise, then drop, it could indicate a sensitivity. If you see a rise, and no drop, or a slow drop, it could indicate a resistance.
Just an idea...I don't know how workable it is, those blood glucose meters aren't exceptionally precise tools, IIRC.