Probably you both really mean the same thing.

Every gram of body weight needs energy to stay alive. If you are in a caloric deficit, you will lose weight until your energy expenditure matches the caloric intake. If you stay in "caloric deficit" forever you will actually starve by definition.

Properly defining what you mean (comparatively low caloric intake without defining it via the current weight) is actually quite tricky, as your height, body composition and physical activities are all inputs to what counts as a "normal" caloric intake.