There seams to be a trend to put T2 diabetics onto insulin. If your control was good on metformin, you could have refused. Didn't you gain weight on gliclazide? I have stopped using it, because it did that to me. If you cut your carb intake, and minimise your insulin, you might reverse the weight gain. What were the grounds on which your insulin dose was calculated? or did they just pluck a number out of the air? there are formulae for this, but since they depend on body weight, you may need to see them again to get it changed. that can lead to the weight gain spiral.