when sugar goes above 300 your body just pisses it out. This causes dehydration and rapid weight loss. I have made a lot of dietary sacrifices...no bread, no sugar added products, no potato, no white rice...very little fruits. I make oat bread from oat flour, and eat oatmeal as it has lower glycemic index.
Can still diet and do more cardio, but have to be careful not to drop my sugar too low or you can pass out...i fell off a treadmill one morning my sugar was at like 45.