According to the gurus of the Master Cleanse, the duration of time is up to you–but a month or more is recommended. This is ludicrous. You are a crazy person who has nothing better to do than sit on your toilet and squeeze lemons if you do this diet for this long. I made it just over a week before I became intolerable to be around, and basically a lemonade-drinking shut-in. Not only could I not participate in just about anything (explaining to a table of friends that “all I’m having is ‘my lemonade’” is harder than you’d think), I never reached the “euphoria” or “lack of hunger” that the Master Cleanse experts describe. And I smelled strange. Like spicy, lemoney sweat. And hunger.
Also, I only lost 3 pounds. Which I gained back immediately, because I was no longer “flushing” out every piece of stuff in my body.
When done “correctly”, the Master Cleanse is supposed to be preceded and followed by a period of time (a few days to a week) of raw fruits and veggies, in addition to the lemonade. This is actually the best/most redeeming part of the diet. Instead of doing the actual cleanse, I would recommend just doing a week or two of the fruits and veggies part, because that’s actually pretty healthy and sane. But if you do just that part, you haven’t really done the Master Cleanse, because you haven’t pooed yourself into oblivion for a period of a few weeks.
If you’re considering doing the Master Cleanse in January, don’t. I can’t, in good conscious, advise you to do that to your bowels, or your friends. If you do feel the need to cleanse, just try cleaning up your food intake–and continue to actually eat food. More fresh food that’s close to the source and less processed crap is more than enough to get your body back on track. There’s no need to juice (and poo) yourself silly.