[k__]

That's around 500kcal deficit a day, which is the recommended deficit when losing weight.

So, yeah, you can lose more than that, but it's probably not sustainable by someone who loves to eat.

[endominus]

Well, depends on the person. Angus Barbieri was able to maintain a 0-calorie diet for over a year, losing 125 kg in the process. Not, perhaps, a feat to be emulated, but obviously physically possible.

https://en.wikipedia.org/wiki/Angus_Barbieri%27s_fast