It's ideal to complete three full weeks on the program, but it's absolutely OK to follow the program for one or two weeks. Every day you will have one solid meal and two liquid meals. The liquid meals will be for breakfast and dinner, and the solid meal will be had at lunch. "Eating the food meal at night will be less effective, because the 12-hour 'fast' that your body will experience overnight is most effective after a liquid dinner, as this frees up the most energy and extends the window of time for detoxification," Dr. Junger wrote in his book.
If you have plans that cannot be rearranged, it's fine to have your solid meal for dinner. Be sure to return to the having the solid meal at lunch the following day. It's imperative you follow the 12-hour detoxification window, meaning if you ate your liquid meal for dinner at 8:00 p.m., you should not have your next liquid meal until 8:00 a.m. the following day.
The liquid meal can be a soup, juice, or smoothie, and should be made by you; this ensures you're only consuming foods that are are the include list. You can also opt to purchase the Clean Program 21-day kit ($475) which includes shake packets, supplement packets, the cleanse guide, recipes, and a probiotic. The liquid meals will provide your body with nutrients in a "fuel-injected way" since they require less energy to break down and the ingredients can be easily absorbed into the bloodstream. Once you have your final liquid meal do not eat anything else after. You can have other liquids, but do not have solid foods in the middle of the 12-hour window.