I think it very much depends on the purpose of the diet.
For me, two weeks of plain potatoes, a little oil, and one piccolo per day was to reset my unhealthy relationship with food. I avoided common toppings (sour cream, bacon, cheese) and anything to flavour them up (salt, rosemary, thyme).
After a couple of weeks, I found I was no longer desperately craving the flavours I previously did. I attribute this solely to the blandness of the food - potatoes being the delivery method is just incidental.