I am on the Betalife diet, and have the same thing happen to me! I have been going for 2 weeks, and have put on weight, instead of losing it. Though they recomend you only weigh once a week, and not get disheartened... though I have been working out harder than I ever had in my life, and feel really RIPPED OFF...Why not just eat the chocolate cake and forget the whole thing, I will get the same result!
I have had a few days off, but will hopefully get back on the band wagon.
Also, I just had to comment on your goal weight being 55kgs. Are you sure that's correct?? I am 157cm tall, and my goal weight is 55kgs, however this will make me REALLY skinny, like a size 10. Many people I have spoken to say around 62 would be more realistic and still allow me to look lovely, and not all caved in. So, are you aiming for a size 8 or something?