here I've heard it described as 'Paleo on crack' 
The long and short of it is: no grains, no legumes, no refined sugar (or substitutes like maple syrup ect), no dairy, no sweeteners, no weird little brownies made with almond flour etc. Just eggs, fruit, veg, meat, fish, nuts (other than peanuts). Cold pressed oils are fine, spices and herbs fine. You do it for a month and most people lose weight and a disproportionate number of inches.
I want to do it because I like low-carb non-calorie counting, but can't manage without fruit.
Today and yesterday have been pretty easy. I made my coffee with coconut milk, which was fine, bypassed the sugar (not so fine but I'll get used to it), and ate lots of nice things. Dinner tonight is roast chicken with a pile of veg. Lunch was smoked mackerel, last night's dinner griddled salmon with mango salsa and asparagus, snacks are fruit mainly, not too much.
But I'm knackered today! Wondering if it's a side effect of the diet. Hope it passes soon.
Has anyone else done this?