No one is perfect, and no one is going to follow any particular diet program perfectly. In fact, it's advantageous at times to indulge in some of the "fun" foods that your program might consider off limits. Some diets go too far in eliminating too many foods. If something is completely prohibited, it's too easy to focus on it. One of the dangers this imposes is that you become obsessed with those "off-limit" foods, which increases the temptation and pressure to eat them. It's fine to have a "cheat" every once in a while; in fact, some programs even call for a cheat day. The truth of the matter is that eating an extra cookie or scoop of ice cream occasionally is not going to sabotage your program. That's why I believe in the 80–20 rule. If 80 percent of what you eat is healthy and on the program and the remaining 20 percent is off the program, you will still be successful at losing weight.
The reason many programs don't want to allow for cheating, however, is that most people don't know when to stop. One cheat can lead to a bigger cheat that leads to an even bigger cheat, and then you're off the program. You have to be the judge of your discipline level. If you're someone who gets a taste of chocolate or french fries and can't stop yourself from eating the entire package or serving, then this method is not for you. You'd be better off following the program as closely as possible with a goal of staying away from those temptations that tend to lead you to overeat.
From The 4 Day Diet by Ian K. Smith, M.D. Copyright 2009 by Ian K. Smith, M.D.. Reprinted by permission of St. Martin's Press.