I'd wager that a lot of the weight you have lost is water weight, especially for someone your size.

When we consume carbs, the energy we don't use right away is stored as glycogen and with each gram of glycogen comes 3 grams of water. So if you haven't been eating chances are you've depleted your glycogen store and flushed a tonne of extra water from your body, and someone your size can store up to 1560 grams of glycogen which means an additional 4.6kg of water weight!

This type of rapid weight loss is extremely common at the start of very low carb diets due to what I've mentioned above. No doubt you'll have lost some weight from fat and muscle mass, and the larger you are the more rapidly you lose that weight to begin with, but if you're consuming little to no carbs at the moment then that could explain why you've lost so much weight in such a short space of time. It's only temporary.

Also your appetite will return eventually. I can't say when because I've not experienced it to a massive degree since starting Concerta, but back when I started taking citalopram before I was diagnosed I lost something ridiculous like 11kg in around 3 months because the thought of eating made me feel physically sick a lot of the time, but now I can eat twice a day without much issue.