Hi sillybillyxo, congrats on starting your first fast, I hope it goes very well for you. Vitamins would certainly interfere with ketosis. The body uses stored nutrients from our own bodies, creates what isn't stored and conserves whatever isn't stored or 'creatable' very efficiently. Adding vitamins to that process would probably stop this process and leave it 'starving' for the nutrients you aren't providing it.

I lost around 30 kilos in the first 2 or 2 and a 1/2 months of my fast and got no stretch marks from the huge shrinkage on my belly. I also recently discovered that the stretch marks I had on my hips, belly and under my arms had all but disappeared. The body will consume excess skin to provide itself nourishment during a fast and also repair already damaged skin.

As for your fears of gaining back the weight, if you follow the fasting principles when you begin refeeding and eat only or mostly raw food in not too great quantity following your fast then the body will only store what it needs and will actually continue with the cleaning out process for a while after your fast. Don't restrict too much or worry about adding the weight back on quickly, if you follow the principles your body will find it's own balance.

I have noticed no problems with my hair during my fast. I have heard of positive changes to the hair though and in particular from getting sunlight onto your hair daily. This should be done especially while fasting anyway and can apparently do wonders for our hair.

Good luck!

Andrew.