Humans are uniquely well adapted to ketosis, whether brought about through fasting or nutritional means
Well Adapted to Ketosis
Starvation and survival.
Starvation in man
Long-term effects of a ketogenic diet in obese patients -https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2716748/
Administering a ketogenic diet for a relatively longer period of time did not produce any significant side effects in the patients. Therefore, the present study confirms that it is safe to use a ketogenic diet for a longer period of time than previously demonstrated.