Yes. I went cold turkey from a bad diet a long time ago, and the withdraw symtoms were very intense the first few days, a migrane headache which I never get.
If you can go raw for a week and try fasting, it will make it easier.

Natural omnivore? What a dumbass.

I would like to add that what Wheatgrass said is true in the sense that if you are looking for permanent weight gains from fasting you had better change your lifestyle after fast with exercise and diet. But would like to also add that really its what you take in for calories and what you burn up that matters and it don't matter much at all if you are vegan, raw or eat pretty much normally even having some "bad" foods occasionally. I am maintaining nicely after very minimal 10 pound or so highest rebound after refeeding and am now at 223 pre fast was 258.8 and lowest weight end fast was 217.2.

I am exercising and you can get more detail on my refeed and intermittent post fast eating style on the fasting for weight loss section of this site.I have not vegan ,not eating raw and not eating totally "correct" foods.