The first 24-36 hours were definitely the toughest, but then the hunger feeling just went away. It was sort of liberating in a sense that I didn't feel "dependent" on food for those three days; the key being to stay plenty hydrated. However, if you're currently working or going to school, I wouldn't recommend it. Save it for a time where you're mentally ready to take on that challenge. Coupled with low-stress and lots of rest, the results were pretty remarkable.
And from the article and science standpoint of it, it makes sense; the less your body has to spend time digesting food (say every couple hours with snacks/meals), the more your immune system can work and more time for the body to naturally repair itself. This is also why I try to avoid eating late at night.