"Of the 229 hunter-gatherer societies listed in the Ethnographic Atlas, 58% (n = 133) obtained 66% of their subsistence from animal foods in contrast with 4% (n = 8) of societies that obtain 66% of their subsistence from gathered plant foods...For worldwide hunter-gatherers, the most plausible (values not exceeding the mean MRUS) percentages of total energy from the macronutrients would be 19–35% for protein, 22–40% for carbohydrate, and 28–58% for fat "
Paleolithic people clearly preferred animal foods as they represented the highest quality nutrition, but only those without the choice to eat plants survived on very low carb diets and the Inuit clearly prized berries when they were in season.
I think a very low carb approach to paleo is as un-paleolithic as a vegan approach. Both can be done and technically fit the definition of paleo, but they are far from optimal. The funny thing as that the people I know on very low carb are often as dependent on supplements as vegans, which doesn't speak much to the suitability of their diet for humans. Although it probably doesn't help that they often don't really try to emulate the diet of successful human carnivores like the Inuit who certainly consumed more than just ground beef. They ate kelp, berries, and a wide variety of meats ranging from fish to polar bear. In fact, arctic foods like smelt and seal are very high potassium and would prevent cramping.