I've starved, not to death and it wasn't my intention at the time either. It lasted for about six months, maybe more. Tbh I liked it. I never felt hunger, not pain, nor any kind of discomfort, I was just blissfully numb. The worst thing that happened was that I was taken to the cardiac intensive care unit when the ambulance I had called for another issue (gallbladder attack) and they ran an ECG and saw clear signs of a heart attack. The doctors didn't find anything except for hypokalemia and I was sent home with potassium chloride. Would consider doing it again, it's just that it takes a while, thus giving your SI plenty of time to kick in and by then you could have damaged your body to the point it's not reversible.
I've also been dehydrated. I never felt thirst (something has got to be seriously wrong with me lol) but after about 20ish hours I woke up with a racing heart and a very low blood pressure, basically had to fight the sensation of fainting, felt nauseous and had a slight headache. Forced down a glass of electryolyte replacement, then I was back to normal in about 30 minutes