Not for everyone, its a bit extreme. Some people can tolerate some plants, but not all people can tolerate all plants.

I personally follow a meat only diet so I can speak to its effectiveness for myself.

In terms of gut biomes we know the bacteria adjusts to the diet - diets high in sugars can have biomes that are dominated by one or two types of bacteria, out competing the other bacteria (and making a diverse biome more difficult to attain).