I've lost phenomenal amounts of weight in short periods on keto at various times, but A: No cheat days allowed or it knocks you out of ketosis, B: No alcohol and C: It's hard to sustain once you're at your target weight.
No cheating for sure! Although my favorite thing about keto so far (week 3) is that it's so easy. I don't crave carbs anymore...at all. Pretty much zero temptation to cheat even once.
I'm on day 3 of Keto! It's not as hard as I thought it would be, but I agree that I don't really miss carbs already. I can see how this diet would work!