I'm not a fan of fasting or "cleansing". The term "cleanse" is vague and poorly defined. I'd need to see some double blind studies that doing so does any good and does not do harm. I think that generating a phobia about "toxins" is manipulative and plays upon the desperation of the sufferer. Nobody names these "toxins" or demonstrates that they exist or what effect they have. People assume they exist because other people assume they exist. It's a dog chasing its own tail.
I'm pretty much convinced that so-called "cleansing", if and when it might have a positive effect, is more the result of the placebo effect and works off whatever psychological component could be adding to the case.
I've read too many cases where "cleanses" have had no permanent effect on this condition, almost all of them, actually.