Sometimes the swf causes the body to retain water and that shows up as weight, a few people have even gained a few pounds on their first MC. The most important thing to remember though is that the weight loss aspect, as attractive as it is, is not the main focus of doing the Master Cleanse. As you cleanse your body you will be healthier. The digestive system in [particular will work much better and more efficiently. If you complete at least 10 days of the Master Cleanse, break the fast properly and then commit yourself to a healthy lifestyle, the weight will come off and stay off. Remember, I did not say "diet", I said lifestyle. This cleanse should reflect a change of a lifetime of habits, not just a short period of time of dieting and cleansing.
If its any consolation, most weight lost during any kind of fast is quickly regained unless there are changes in lifestyle. Most of the initial weight loss reflects the loss of bowel material and excess water. Relatively little fat is lost in the first few days. Its what you do after the Master-Cleanse ends that will make the real difference. The only time I would suggest The Master Cleanse as a weight loss program only is if you need to temporarily drop a few pounds, because you will quickly regain most of that weight.
To give you a little short term help, try not doing the salt water flush for a few days. Drink extra plain water with a little fresh lemon juice in it to help cleanse the kidneys. If your problem is water retention due to the swf, then you should experience a little weight loss as excess fluid is flushed from your body. I cannot do the swf because it makes my blood pressure spike. I have a feeling quite a few people may have problems retaining the salt water.