You should watch the documentary "Fat Sick & Nearly Dead." This is about nutritional intervention of disease. The filmmaker was over 100 lbs overweight and suffered from a debilitating autoimmune disease. Doctors held little hope for him. He traded his junk food diet for a program of only vegetable and fruit juices for 60 days and regained his health loosing most of his excess weight and overcoming his disease. I did fruit and vegetable smoothies (smoothies using the whole fruit include fiber that is mostly removed by juicers) for 3 weeks and it went pretty well and in the month since I've been eating one or two normal meals and having smoothies for the rest of my meals. I lost 15 lbs and my cholesterol is the lowest it has ever been so it worked out well for me. If you are interested in this I'd encourage you to check out the documentary. There is some debate about the merits of juice vs smoothies. Juicing you can consume more nutrients since you can consume the juice of more produce than you could in smoothies but I lean toward smoothies because a lot of the nutrition in fruit and vegetables in in or near the skin and the fiber of course is good for you.
it's not advisable to do that to be honest, even extreme diets such as 'lighter-life' and the 'Cambridge' diet introduce solid food relatively early on, also they are constantly monitored by a professional!
what do you hope to gain by a purely liquid diet?
also, over a long duration it is bad for your digestion and the activity of your bowels. you would need 'some' solid food daily for roughage.
if it is for weight loss, there are far more efficient ways to lose weight, whilst maintaining a normal diet.
Basically these will will happen:
If you replace solid foods with liquid food (protein shakes etc.) then you'll just feel less satiated and will want more. If it's not, then you'll create a diuretic where you'll lose lots of water and/or muscle weight.
Your body will be cleansed of toxins, but without any nutritional value of water/juice, you'll lose unhealthy weight and may get sick.