I would recommend newcastle diet, as it improves insulin sensitivity and it is very good for people with diabetes.
sorry, in this case I disagree, Catsbd, the original poster says she has had Type 1 diabetes for 40 years , the Newcastle diet is aimed at people who have T2 , Dr Taylor specifically says that it is not for T1s.
I also think such a low calorie diet would be very difficult to manage in terms of getting the insulin right. (and just about impossible if the original poster was on a mixed insulin regime)
Catsbd,
I'm assuming that you take a basal insulin and a rapid insulin for meals and are experienced in adjusting them.
The official Slim fast plan includes 2 shakes, 3 snacks and a low cal meal. I think that this could be difficult because those snacks are 15g carbs. If you don't inject for those snacks your glucose levels will rise beween meals, if you do then you run the risk of stacking insulin. If you miss out the snacks to avoid the problem then you will reduce your daily calories by 300 and end up on a very low cal diet and possibly hungry .
Edit: I've just looked back through your posts, I think that you should perhaps ask discuss this with your doctor or even ask to se a dietitian since you have had some problems with low iron levels and that may (don't know) be something to take into account.
To be honest, I agree with Sid that you need to look for an eating pattern that will work for you and one that you can keep up. I also think that one of the best ways to increase insulin sensitivity in T1 is to increase exercise.