"They didn't eat fatty cuts of meat, they ate super-lean meat when they could catch it."
I take it you've never butchered a whitetail deer. Or a raccoon, a squirrel, a pigeon, or a dove, to name a sampling of wild animals not changed by breeding programs-- essentially the same as they were 150k years ago. There's plenty of fat in wild game. In fact, the lean muscle meats where generally the last part of the animals that people ate. First they ate the liver. Then they ate the other offal and brains, including the large globs of abdominal fat. And catching wild animals is really not that hard.
Also, there are hundreds of edible plants which have not been farmed and selected by breeding programs over the millennia, such as cat tail, sea weeds, stinging nettle, and black walnuts.