Yeah its a terrible way to lose weight, that's why stickies on places like bodybuilding forums encourage a moderate deficit plus exercise to maintain bone and organ health (1). But it goes to show that with a deficit you will shed weight. There is no special sauce in individual metabolism that makes energy from nothing at the end of the day. Losing weight is a matter of thermodynamics.

1. https://forum.bodybuilding.com/showthread.php?t=165843261