well, you can expect to slow down our metabolism...it's only normal. And anytime you lose weight, you inevitably will lose muscle as well...the important part is theafter-fast.
it's great to go onto juices after a water fast...and if for a whole month afterwards you stick to a fruitarian diet, expect to increase your metabolism after just one month. http://www.thefruitpages.com/
then, you slowly try and incorporate a raw vegan diet...and then IF YOU WANT, you revert back to old ways..but don't think that way ;)
good luck on your fast...if you need support, I'm here for everyone