I just looked at those images
http://www.colondiet.co.uk/mucoid_plaque_photos.html Pretty bad stuff...
Through a "cleansing diet" or juice fast, 3 forms of weightloss will occur:
1. Your intestines will be emptied.
2. Water weight.
3. Fat/muscle loss
Most of the time the majority of the weight lost will consist of the first two. This is why people regain most of their weight after they start eating again.
The problem with longer juice fasts is the lack of protein, combined with (very)low calories which will cause muscle breakdown. 50% or more of the weight lost over prolonged fasts may be muscle (this also depends on current levels of bodyfat for one, Men with a bodyfat% of 15% or lower will lose muscle at a faster rate than at 25% bf) And remember a pound of fat equals about 3500 calories, losing a true 2 pounds of fat per week on a diet is already quite an achievement for most people and will require a pretty(very) restrictive diet. Claims about losing 10 pounds or more the first week are
never due to great fatloss, only a small percentage of that will be fat.
So if your goal is to 'cleanse' your intestines, go for it. But if you want to lose weight get on a proper diet with adequate protein levels, and not a juice fast.
Though 'cleansing' is not at all necessary for healthy individuals who are eating well.
http://www.mayoclinic.com/health/colon-cleansing/AN00065
I would only consider it if I'd been leading a very bad lifestyle and/or was heavily constipated.