There is a variety of Type 2 called ketosis prone type 2 DM, or Flatbusg DM after the area of USA where first described. When the person's glucose level goes high, the beta cells switch off insulin production and they restart when glucose levels have been controlled for a bit. 50% of new presentations of DKA in African Americans actually have this and although much more common in Afro-Caribbean folk, it does occur in Europid people. So this is possibly what you have and what you have treated with your weight loss. The GAD antibodies look at the cause of the problem, you could always look at urinary C-peptide to see if making insulin. But as others have said above, probably most important is to continue with the low weight and to monitor progress.
Best wishes