How to lose pre-op weight with insulin resistance

It seems almost impossible to lose my 20 lb pre-op weight.  The barrier is the insulin resistance.  Does anyone have any suggestions on what I can do to drop this weight.  My surgery is halted until I do.  I exercise, I eat 1200 calories a day and the weight just isn't coming off. 

What are you doing for weight loss?  I was in a similar boat and used protein shakes.  I lost 20 pounds in 2 weeks.    I took in about 600 calories per day  on the shakes.

I am 7 weeks out and no longer need insulin.

Steve