Juice fasting!
Juice fasting is awesome. Over the years I've done every type of detox imaginable. Liver flushes, parasite cleanses, herbs, bowel cleanses, colonics, etc etc etc. Nothing has ever compared to the benefits I've had from juice fasting on green juices. I felt better than I ever had in my life after a week long juice fast last winter, and the summer before that, I did a 15 day juice fast that left me on top of the world.
I am already thin, and I don't do these cleanses to lose weight. I do them to help heal my gut. I have leaky gut disorder and a lot of damage to my body from gluten and other things (I'm a celiac). Juice fasting gives my gut a break while infusing my body with tons of enzymes and nutrients. It's just amazing.
Although most of my fasts have been longer, I am now experimenting with doing shorter fasts when I can. Three days is generally a good length of time to get a little detoxing done, rest your system, and kind of reboot everything back to a healthier baseline. You may lose some weight, although I never lose weight when I fast. It's a great way to transition onto a healthier diet as well.
Good luck!