Doctors can keep people alive in comas for decades, we've got plenty of proof for that.

If your goal is to be "alive", then sure, it can be done using supplements and your body fat reserves - we've also seen a few cases of this.

The amount of permanent damage you do to your organs and brain, however, is unknown. How the extreme starvation feelings will rewire your brain is unknown. How your body will react when you start eating again is largely unknown.

Unknown is scary for doctors, they avoid anything and everything that isn't in their handbooks - for good reason! People sue people on a whim.