Optimal diet for most people


On episode #469 Steve says that, for the average person, or most people, the optimal diet consists about 90% of this: "Eat a variety of food, a lot of plant food and not too much."

That sounds very reasonable, but doesn't the "a lot of plant food" part of it exist only because nowadays we eat too little plants? If we lived in a society where people would eat mostly plants, wouldn't that be replaced by "a lot of meat"? I mean, as a general rule, that sounds a little confusing to me. And, as a general rule, I find it too hard to find similar data on the webs.