The most "radical" concept of this way of eating is getting rid of grains and legumes. I find this no more radical than claiming we need the majority of our diet from these two groups of "foods." Taking the time to really look at the nutritional "value" of these two groups of foods shows you that they are pretty much a terrible way to get both macros and micros without getting fat.
If you look at the way people ate just 50 years ago, we adhered to a three meals a day model - not six small meals which never sate. Snacking was for children mostly (often two cookies after school) and then those children went out to play before dinner was ready - they didn't sit in front of a screen. 50 years ago, about 10% of the population was overweight. And the foods we ate, were largely wholesome.
Obesity in this country (and as always, we led the pack) started to climb with the proliferation of:
-processed (convenience) foods
-CAFO foods being the majority of what was available to the average consumer (only CAFO chicken was prevalent until about the 1970s)
-produce shipped an average of 1500 miles before the consumer gets it (loses nutrients every mile it travels, and some estimates are that the nutrients in veggies that our grandparents ate have decreased by up to 40%)
-HFCS and soy becoming ubiquitous in the food supply.
Add to that, a government that told us fat was bad (the same govt that declared catsup a vegetable back in the mid 70s) and that eating like rabbits was better, and obviously (to me anyway), what's not sustainable to the individual is what we've been doing for the last 30+ years.
Anyway, that's my take on it. For me, this is like moving forward to the past, when food actually fostered health instead of being the cause of disease.
I won't go into the sustainability of farm vs CAFO here, but there's plenty of info if you google. The govt has their side, and the whole foods people have theirs. I encourage you to look at both.