Been experimenting with dirty fasting and caloric restriction. Whether I eat 10, 20 or 67% of normal calories, I lose mass at half the rate of a strict water fast (0.6 lb / day vs. 1.2). Kicks you out of ketosis too often.
OTOH, you keep your normal energy level, so it’s way more pleasant and sustainable. Your hands and feet are cold, but not much hunger. And you don’t need to drink salty electrolytes as much.