It's the fact that this diet's leading proponent was morbidly obese. If the man who thought it up couldn't stick to it or make it work, what does that tell you about what he thought of its worth?

The bad breath and not being able to produce anything that one would ever describe as "too beautiful to flush" were enough to turn me off it (ask Scott about the necessity of a vegetation-heavy diet in the production of world-class grogans). My brother-in-law also lost loads of weight on it, but once he came off it (at the insistence of my sister), he put all the weight back on. Interestingly, his mood improved markedly once he started eating normally.

(Edit: Mentioning Scott made me think that he should market his diet. The man's a twig. The "World-class Grogan And Really Thin Veggie Diet", or something.)

It's like all extreme/rapid-weight-loss diets - a bad idea.

Eat sensibly and get some exercise. If calories expended > calories eaten, weight loss will result. Ask any dietician or nutritionist - the unpopular truth is that there are no easy long term answers, only self-discipline and exercise.

Also, while experts are not completely unanimous, it's the general opinion that more fibre helps to protect against colorectal cancer.

And I don't want to be killed by my own arse.