Dr. Gregor has great understandings for vegan/vegetarian intake. I've listened many of his youtube vids and lectures.
And yes, this general "Daniel and his cohorts" approach works fantastically well. In short (there are many variations) it calls for elimination of meat, fish, eggs, dairy, wheat products, processed oils and processed foods. It's nearly impossible to eliminate every avenue of processed oils when dining out, but a dramatic reduction of intake is easily achievable. At home I use coconut milk/shredded organic flax seeds for moderate oil/fat intake, and organic cold pressed organic avocado oil in small amounts for stir frying.
You can all all you want of what else remains and NEVER feel for one moment like you are starving. And weight loss follows. It's truly amazing. I just got back from a several day trip out of state for a wedding. My wife still eats a SAD,
(standard American diet.) But we managed to eat once a day, usually mid afternoon, at buffets where I could have unlimited amounts of fruits, potatoes (usually with meatless marina sauce), vegetables, mushrooms, onions, peppers, greens of all sorts, etc. Seriously ate like a pig. At the wedding they had potatoes, vegetables, salads, etc. Just avoided the meats and cheeses stuff. Even had about 4 micro brew beers. Returned home and voila, not a pound added. It's wonderful and easily maintainable.
I'd recommend it as a permanent diet change for anyone. Particularly to anyone suffering various health or weight problems. The Daniel 10 day was probably just veggies. But for long term viability some starches need to be included to make it successful, such as potatoes, sweet potatoes, rice, etc.