With this diet, you aim to eat healthy, whole foods 80% of the time. It's more of a lifestyle rather than strict guidelines. While being unhealthy the other 20% isn't encouraged, the focus is more on the 80% time. 

What you can eat: whole, unprocessed foods like fruits, vegetables, proteins, and healthy fats

What you can't eat: Really, nothing, just as long as long as it doesn't surpass 20%