Definitely wait until your holidays are over imo - and yogurts of all varieties are out until a later stage of the diet. Have a good read if the book when you're off relaxing and see if it feels right for you. As far as I'm aware though ketosis is definitely not the reason your hair thins on a vlcd - fast weight loss is. It's called teflum effluvium and can technically happen on any diet although with vlcd it's most common as the loss is so dramatic and you're not getting enough calories for the body to put into hair growth. But it basically just means you've shocked your body with the sudden weight loss - it will grow back. I think it's usually a 3 month cycle if I remember rightly. It can happen after surgery and after giving birth, too.