I lost 4.5 stone and dropped my A1c from 10 to 4.8.
So yes it can be done, by diet and excercise you can be almost normal, but if you start eating loads of carbs and not excercising it will simply come back.
I am that proof, I managed for 8 years but eventually the weight came back and now I am on another diet. I have still got my A1c down to 5.2 by diet and excercise, but I am now on Metformin.
You can delay it, and I, and lots like me, have done it, but it is always there just waiting to come back and bite you in the bum!
So do what you can while you can, expect to progress, but try and do ikt very slowly, you live longer then.
H