As a PescePaleo I will say that there is a lot of truth to what they found and it should not be dismissed. I have Inuit genetics so you would think that I would need low carb, but that is not true. You see my people used to get a lot of carbohydrates from fish and raw seal meat. Both or which can contain up to 30% carbohydrates in the form of Glycogen.

See, since we have low CPT1A genetics we do not get the same energy from ketones as all you farmers and southern Hunter/Gatherers do. As a result we need these carbohydrates to to fend off fatigue, behavior changes, and low blood sugar.

So the U shaped curve makes sense, at both high and low ends of the spectrum there will be people who do better. And remember, Paleo is NOT Keto!