I have read Lyle's Ultimate Diet 2.0. He kind of backs up my points quite well...
And, under certain conditions, ketosis has potential benefits.
One is protein sparing. Arguably the main reason the brain shifts to using ketones during
starvation is to reduce its reliance on glucose; this means less body protein needs to be broken
down to make glucose. In studies where protein intake is too low, ketosis may also be protein
sparing.
However, UD2 doesn't actually get you into ketosis, or at least it's not concerned with it. Granted UD2 is considered a cyclical ketogenic diet, it's more of a caloric cycling diet - where you go from periods of extremely low-calorie (50% of maintenance) to very high-calorie. The carbohydrate levels are not the heart of the conversation with that book.