Who or where did you ever get the info that LCHF was that low a calorie intake per day?
that is a very high loss for a short time.
you are only eating 1/2 what you should in a day... the weight loss will slow down but be sustainable.. and healthy..
If you enjoy the LC way of eating, I would suggest you go to the Atkins site or get the books and look at how that eating plan progresses from induction to slowly adding in more carbs and finally on to a life plan.
If it is a plant, eat it, if it comes from a plant, don't!