Pre-op: weight going down, body fat going up?

I've been on the pre-op diet since Monday. I've lost 6.2 lbs so far (I know, most of it is water weight but it's still fun!) but my body fat has been steadily increasing every day (I have a scale that calculates it). I know the scale isn't 100% accurate on body fat, but I've never seen it go up so quickly and so steadily (usually it hovers around the same number and if it goes up one or two days, it goes down the next). Is this because of the pre-op diet? Burning beloved protein instead of the hated fat? I am not exercising yet (too busy working trying to get everything done before surgery).

TIA!

There is no way on those pre-op diets that you dont lose a lot of lean tissue. You simply cannot lose body fat that quickly and that's the truth. THe only reason that Optifast etc is worth doing is for the liver shrinking, in no other way is it beneficial to your health. In the case of this surgery, shrinking your liver if it is large and fatty is of prime importance and outweighs the downside of losing lean body mass.

That's why these diets are never an answer to long term weight loss

It's not that the actual amount of body fat you have is increasing its that the percentage of lean/fat mass is changing and also you're losing a LOT of fluid (that's where the fast weight loss comes from).

When I brought up with my doctor that after 3 days on Optifast I was fainting, he told me not to do it. He'd told me I didnt have to and I decided I would have a go anyway and he told me that it was pointless as my liver was neither large nor fatty and that it would be of absolutely no advantage to me to do Optifast for any other reason.