Be careful. Depends on what you mean by "diabetic" Type II diabetes is an incredibly popular diagnosis that has been expanded to cover a LOT of things that are in fact very different physiologically. For many of these the "usual advice" is counter productive and even dangerous. But for a lot some generic things still work - but things like fasting are very bad.

If you are type I, as in pancreas doesn't produce insulin, things like fasting can be very, very bad (as in fatal). If your pancreas is dead, this will not be reversed by diet.