Yes I did a juice fast for 35 days in May and actually my dark circles got worse- they spread up to the inner sides of my eyes.
I probably didn't rest enough but I really didn't enjoy that fast and my skin showed no improvement which I though was weird. Most people get smoother skin on a fast.
I like the idea of Water Fasting though, but I dunno if it would help me. At the moment I'm getting some small results from Iodine so I want to keep going with that.