1200 is probably too low pet.. you might be at risk of your body trying to store fat x
Believe me, I had a condition called hyperemesis when I was pregnant as was unable to hold food down properly from about 5 weeks till around 20 weeks. In that time I lost nearly 2 stone, but most of it was in the first few weeks of it. I stopped loosing weight after a while, even thought I was probably on about 500 cals a day max (mostly less than that I'd guess).. and most of that from full sugar drinks.
Once I was able to eat again I was diagnosed with gestaional diabetes and started eating well and maintained that weigh for the rest of the pregnancy pretty much - I was 2.5 stone less than I started shortly after giving birth. So I have first hand experience of weight loss stopping weightloss by eating too few cals.
Everything I have read says you should really be eating 1300-1500 to be following a decent healthy diet.
I have to say, after that experience I would never ever try a VLCD. Ketosis is not a good place to be in x