There has always been something psychologically unhealthy in all dietary regimens that revolve around self-denial. There's a sort of desire to feel that one has elevated oneself by taking a peculiar sort of self-denial (of whatever-- meat, carbohydrates, or, lately, simply calories
) as an end in itself.
Long before Nietzsche, Montesquieu said of monks that they cling to the denial of their passions with at least as much force as those passions themselves would have if they were given free reign. Apparently it's no longer fashionable to mortify one's flesh for the sake of eternal life, but the doctors assure us that to do so in the name of the partial extension of one's mortal life and a longer old age is to be praised.