I am a doctor and type 1 diabetic. I also gained too much weight by anabolic effect of insulin and overdosing. I lost 42kg in eight and half months by reducing calorie intake mainly refined carbohydrates and reducing insulin but also keeping control of blood sugar. I am now having ideal bmi. Dont lose hope and keep trying.
Solution is simple. Dont overdose. When you overdose, your blood sugar will get low then you ll eat more and gain weight. This is a vicious cycle. It takes lots of efforts to get out of this cycle. You ll have to keep control of your diabtes too while loosing weight otherwise you ll get complications.