It's a very small study but all of the participants had their insulin levels return to normal.
small excerpt - if you're interested, you need to read the article.
The results of the diet
Under close supervision of a medical team, 11 people who had developed diabetes later in life were put on an extreme diet of just 600 calories a day consisting of liquid diet drinks and non-starchy vegetables. They were matched to a control group of people without diabetes and then monitored over eight weeks. Insulin production from their pancreas and fat content in the liver and pancreas were studied.
After just one week, the Newcastle University team found that their pre-breakfast blood sugar levels had returned to normal.
A special MRI scan of their pancreas revealed that the fat levels in the pancreas had returned from an elevated level to normal (from around 8% to 6%). In step with this, the pancreas regained the normal ability to make insulin and as a result, blood sugar after meals steadily improved.