The Paleolithic diet-- removing all modern farmed livestock (like farmed beef, chicken, pork) and going back to wild game, beans, and things that one can gather like berries and nuts.
It's a tough diet to do. I tried it once. The hard part is finding the wild game. Where I live there's really no wild ducks, no deer...it's near enough impossible to do in the Arizona desert. Most I could do was Quail and Rattlesnake. So I had to give up on it. There was an Ostrich farm between Tucson and Phoenix--but they are farmed ostrich. Deer meet around here is sometimes farmed. What I really wanted to try for wild game was Gazelle. Apparently gazelle used to exist in Europe and the Middle East during the Ice age but was one of the first foods hunted to extinction on two continents. Africa is the only place with gazelle left. I figure they must be super tasty if humans ate them to extinction on two continents. Got to be better than deer which is still everywhere.
Anyhow, after calling every grocery store in town, Whole Foods gave me a flyer of where they sometimes get some imported meats. And this guy had everything--any kind of wild animal from around the world and the permits to sell the meat in the United States. But, when I asked if I could buy some gazelle steaks--he started laughing at me. He says that I'd have to buy the whole gazelle, they would deliver it to my doorstep and I would have to butcher it myself. I don't have a chainsaw and not enough freezer space to store an entire gazelle...so I gave up on the whole idea of the wild game Paleolithic diet. I tried...it was just too difficult to get the wild game imported to the desert.
Most people who do the Paleolithic diet have Multiple Sclerosis. There's people like Matt Embry who were crippled, wheelchair bound with Multiple Sclerosis that went on the Paleolithic diet removing all farmed foods that were able to walk again--full remission--when on the diet for 2-5 years. It's just a really difficult diet to do.