Do you guys know anything about this plan?
I have seen online that Joel Friel modified and endorses this type of eating for endurance athletes. It raised a few flags with me, but I wanted to see what you all thought.

If you are not familiar with it The original says:
Lots of lean protein, fruits, veg, seeds, nuts, olive oil
NO-grains, dairy, sugar,potato of any kind

The Athletes version allows for high glycemic foods during and after exercise, and some foods like sweet potato. But still no dairy or grains of any kind.

I already avoid processed foods, and hydrogenated outs, junk etc.
But no dairy or grains would be really tough for me. And is that good? Just because our ancient ancestors did not eat oatmeal does that mean we should not? Sometimes progress is not a bad thing. Maybe they would have scarfed it down if they had it available to them.