It's the Scarsdale Medical Diet, a low carb diet formed in the 70s/80s by a doctor to help heart patients lose weight. It's only meant to be done for 2 weeks at a time (2 weeks on, 2 weeks off), but its apparently guaranteed to help you lose up to 22lb (10kg) in that time.
Here's a link to the actual diet:
It's based on the idea of Ketosis, which apparently helps you burn fat quicker. I don't fully understand the concept, but hey, it works! Its apparently dangerous to stay on it too long because it cuts out a lot of good fats, and plus you need carbs to survive. But I think I will keep up with the low carb thing.