There was a story on here a few months ago about a 600 cal/day diet that reversed diabetes in a few weeks.
Anecdotal story:
http://www.dailymail.co.uk/health/article-2385179/I-reversed-diabetes-just-11-days—going-starvation-diet.html
I imagine that will be temporary. As we age, all our systems break down, and for people with diabetes, it’s the pancreas that goes the fastest.