Well, first, we should be talking about a high vegetable diet!
Fruit is way behind vegetables in high nutritional content.
Previously, I mentioned the "Eat to Live" book and I can't recall Dr Fuhrman saying that his diet would not be healthy for certain types of bodies!
I am blessed with a constitution that can eat anything, and "green" smoothies are the main stay of my diet.
However, I know lots of people who say that their bodies couldn't handle my diet, and, I accept that switching to my diet, suddenly, would literally have lots of people doubled-over with stomach ache - or never out of the toilet!
However, I do believe that gradually switching to such a - very healthy - diet could be done, by degrees, over as bigger time period as is needed.