Starvation and survival.

G. F. Cahill, Jr and O. E. Owen 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2441175/

Starvation in man

https://pubmed.ncbi.nlm.nih.gov/4915800/

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.