I am firmly convinced it is. Early man did not store food. The only substantial real source of carbs during the winter was roots which have to be cooked. Cooking utensils per se (pots) have not been around that long. Man went into ketosis for months at a time! It is a natural state. That is why it feels good (all but the most extreme levels). Ketosis is a benficial state. It alleviates depression, makes you more alert, reduces hunger, gives you energy etc. All this with the side benefit of burning fat at an accelerated rate.
I have literally been in low level ketosis for months at a time.
Was sad to hear that Atkins is in very bad shape. He made quite a contribution, and rec'd little scientific credit. His books are some of the most readable of any I've read on nutrition. He did make a BUNDLE, thought!!