If you're looking to cleanse your body of toxins, make it simple and stick to water, fruits, veggies, and simple proteins (eggs, beans or meat) for a healthy jump start. Ignore all the claims about colonics that cleanse your body of toxins. If you are really ready to work hard to increase your energy levels and improve your health, then the cleansing diet you want is simple: stick to fruits, vegetables, and a protein source at every meal and snack. Eliminate processed foods. Skip anything with high-fructose corn syrup and every other additive or chemical that you cannot pronounce. Drink water -- add a lemon or lime slice for a change of taste now and then.
If you are serious about eliminating toxins, give up caffeine, alcohol, and artificial sweeteners, too.
How long do you have to stick to this supercleanse diet? Start with one day, and see if you can't last several days. If you really want to jump start a weight loss program, commit to a whole week.
This is not a very low-calorie diet that requires medical supervision, and it is not dangerous in any way.
Do I think you need to live on this forever? Well, you'd certainly be healthy if you did.