The body is designed to detox itself (from a cavemans diet) but in many cases it can get too overwhelmed to do this efficiently. There are 2 phases of liver detox - first breaks down the bad stuff, the second removes it. When you have people whose stage 1 detox is working better than stage 2, then you have some pretty lousy feeling people walking around.
Detox diets have been touted as a cure all but sadly there is mostly only anecdotal evidence to support them. I used to prescribe them a lot when i was practising, but my field was pretty narrow - I spent most of my life as a naturopath working with kids with behavioural problems (ADHD and the like). The diets would make varying degrees of difference in about 65% of the cases I saw. Most spectacular result I saw was in an older lady who had bad osteoarthritis (could barely close her fingers, walking was hard). She came as a last resort and didn't really believe in anything. I asked her to eat nothing but a selection of steamed vegetables, fish and plain rice for 8 weeks. She was allowed to use sesame oil for flavour. It was a battle to convince her to do it, but she was a completely different person when she came back in.
Bottom line - they CAN work, but most people touting them have an agenda. I actually think fasting is a better more efficient way to achieve the same results but here again, you're probably only going to find anecdotal evidence rather than hard and fast proof.
