The problem with a calorie limit, is at first it seems very reasonable. Well I just do 1000 calories to lose weight fast - no biggy. It wont get bad. It will be ok.
But then you don’t even notice how 1000 turned into 800, and 800 into 700 and just a short time after you are under 500. And suddenly you only eat once a day and only because you have to and you work out like crazy so really you are at no calories and your hair is falling out.