Not a complete answer but 3 million people took the Cambridge diet in it’s killing form (powder and milk equivalent) and 50+ died of complications. Very few if any were under medical supervision, many were likely desperate and metabolically challenged, needing little to tip them over the edge due to one physiological weakness or another. Bariatric patients are medically supervised, fully tested for issues before the process etc. CD takers often did this for many weeks at a time while most EF is <5 days.
Remember keto EF should only really happen after being fat adapted when the body’s reaction to it is very different and far less stressful than mere calorie restriction. It is not a front-line strategy nor is it focused on weightloss but a follow up approach to reduce insulin resistant set point and invoke autophagy. Keto EF is also typically properly supplemented, especially if it goes beyond a few days, primarily in the electrolytes area or else you do risk catastrophic heart complications etc., especially if you have a weakened heart.
Isn’t it strange how not eating at all can be so much safer than consuming some highly processed chemicals? 
