That's a pretty good time, so the diet seems to be effective. I have not built up to a marathon yet and it still seems like a big jump from a half, but seeing what others can do gives me some faith that I could do it, although I would not be anything like as quick as you.
Go for it! If you double your Half-Marathon time and add ten minutes, the result will be a reasonable target for a Marathon.
I'll try building up my runs and see how it goes