I imagine it depends on so many different factors.

I tried longer fasts (for health rather than weight loss), and I loved how I felt during the fasts themselves but then afterwards my hunger signals were often messed up for over a week. I'll try again once I'm more settled with carnivore.

Do you use intermittent fasting? I don't hear the same dramatic health results but I think they probably accumulate, and a lot of people use it for weight loss.