Sound like an eating disorder more than anything else. Unless this person is quite small doing just 3 drinks a days they are probably dehydrated and definitely so if they are not drinking a good amount of water along with those 3 drinks. Because of the low caloric intake they are prolly slowing the metabolism more than they would be at least doing the minimum 6 drinks.
If they're slowing the metabolism more than usual then eating then starting again that does not sound like any kinda of a good or healthy idea to me.
The best thing you have going for you is that you have the correct attitude for success since are approaching the weightloss issue from a health perspective and not like the vast majority of "dieters" that frequent this forum that all they can talk about is "weight loss" and the numbers on the scale. Permanent weightloss will require a lifestyle change and the addition of regular exercise and the MC is and excellent headstart to clean out the system so it will operate more efficiently and you can continiue to loose weight safely and effectively by the required lifestyle/diet changes.
No form of fasting was ever designed for loosing weight. It just a tool and with your attitude and overall aim of achieving "health" rather than focusing on weight and looking at the numbers on a scale you have a winning recipe. You'll hafta cultivate patience as it will take time. Keep reading and education yourself about nutrition. Lots of good info on this site.
I can't stress regular exercise enough. This is where you will really start seeing the body reshape itself and the weight drop off in a healthy manner and not some quick weightloss fad like most "dieters see the MC. If you really wanna see some results include resistance training in your exercise routine. Muscle burns fat!!
Forget the yo yo MC method that some describe. Do all the cleanses and that will take the trash out. After willl come the rebuilding through nutrition and regular exersice. Prolly the best single thing you can do for your health nutritionally will be to get a vegie juicer and drink fresh juices everyday.
Personally for me to do the MC where it will really do some real cleansing at the cellular level 15 to 21 days is minimum. Read the Detox stages in the FAQs (http://curezone.com/forums/fm.asp?i=265174#i ) for an idea of the cleansing time line.
Don't let my recomendation for the 15/21 day thing scare you. Bottom line this is you first MC so you play it by ear and do the best you can. For me I dove right in and did a 40 dayer from the gitgo and it was the most amazing experience I've ever had in my life. The mental aspects far outweighed anything else.
If you are really in for the long haul you might want to do a pre cleanse diet of raw food for a couple of weeks pre MC to get you system gradually detoxing. This will minimize any harsh detox symptoms and make it easier to go past 10 days. Some folks have even done one month of eating raw and vegie juice to get the most out of their MCs. I credit that what really helped me breeze through my first 40 dayer was that I happened to be on a juice fast and after around 5 days I was doing some research and found this forum and just knew that the MC was for me and switched over thus my system already had been on a 5 day juice "pre cleanse".
For more insights on the MC and weightloss check out this in the FAQs
http://curezone.com/forums/fm.asp?i=265185#i
Keep up your insightful winning attitude and best of luck to you.
I'll remind you though that the make or brake of your quest for "health" will definitely >>NOT<< be the Master Cleanse, that's just a good start. Your real success will be based on what you do >after< you clean the junk out. I you go back to your old diet/lifestyle you will loose all benefits including any weight loss.
While you're fasting it will be a great time to educate yourself on nutrition and either plan some daily exercise or start looking for a gym or aerobics class in your area. The hardest part about exercise is getting started. You might hafta force yourself at the beginning but combined with a good nutritional program you'll start feeling so good you'll become addicted!