This is an awful lot like doing Optifast, which was popular in the 1980's. I did Optifast briefly myself, and it was powerful in the short term. The protein does curb the hunger to a certain extent.

The problem for me was refeeding. I kept the weight I lost off for two years, which is good, but rebounded after that.

I think that doing Atkins is much better because of less deprivation overall. I would guess that similar results could have been obtained with more fat and more exercise.

Very low calories have been shown to extend longevity in other studies on primates as well, but I don't think it is a happy way to live.