In my practice I encountered two patients that were officially cured.
One had pancreas transplant that caught.
One did it by rigorous diet and exercise.
That being said, I work with people with diabetes for 21 years.
Diabetes is 100% preventable or manageable with diet and exercise. Unless there is damage to pancreas.
But, most of the time, it is result of very poor diet and very sedentary life style.
Bigger problem is, diabetics loose sense of reality and gravity of their condition. As Dr Campbell called it, they get "diabetic euphoria". Part of this is impaired sensation due to peripheral neuropathy and lack of pain. Part is poor vision and lack of visual feedback. Part of it is simple shift in mental functions. A lot of it is being immersed in culture that hammers you with eating crap, lack of good quality products, lack of strict enforced prevention programs and screenings.
In native Indians it's a disaster.
Diet should be geared towards a little carbs as possible, as they are most easily cycled into blood glucose. Exercise should be rigorous. ONE HOUR of very vigorous exercise EVERY DAY. Weight should be hawked constantly. Weight goes up - blood glucose goes up.
Here's a fantastic resource for those who want to step onto proper diet path:
https://archive.org/details/diabeticcookeryr00oppeiala
Also, before someone jumps at that book with fiery sword because it "promotes too much fat" don't forget, that this year, dietary guidelines were finally revised for the first time in 50 years to say that fat is not bad, neither is cholesterol. 50 YEARS of lies.