that video is an example of an eating plan that worked for 3 people. like any other fad or diet of the month , it works for some and not for others, at the end of the day, my take on it: our bodies, and our emotional health is very much reliant on what we consume. These 3 people seemed to have cut out a bunch of other bad stuff, not just greens. My layman opinion if you only eat one category of food, as long as it's natural and not something like say McDonalds, yes you will be healthier, you will lose weight (probably because you're bored of eating) If you're following a vegan diet for health reasons, it may not work for everyone, but if you're doing it out of empathy to sentient beings being used as food, then yes, it works. Every bit of less animal product consumed will make a difference in lessening the suffering of animals. Apparently in South Africa 19 million chickens are slaughtered a WEEK for food. That madness.
