I vary it almost daily. Mostly 16:8/18:6… sometimes 24hrs. There’s no way that can mess anything up - what matters is what you put back in at the end of a fast (i.e. don’t overeat). I’ve lost around 6kg since the start of December, and I never feel hungry. Make sure you’re using electrolytes and mineral supplements… make sure you stay in calorie deficit, but don’t starve yourself.