Search, and it is not hard to find accounts of those who died almost instantly after breaking a fast in foolish fashion.
What enters the body post-fast is far more important than the fast itself.
And why is being a vegetarian relevant? (One who freely consumes dairy and cooked food is hardly apt to comment on matters pertaining to purity of blood!)
Perhaps you can experiment: fast for forty days on distilled water and small amounts of orange/lemon juice (only when deemed necessary), and then inform us of your progress once you have broken said fast with burger and fries (or grilled cheese, fried bread, or whatever plague takes your fancy). I am prepared to change my mind if you survive...