The Cabbage Soup Diet: Quick Fix or Health Risk?

Any diet that has you eating the same thing all the time is gonna have some inherent problems. Your body's needs for various nutrients varies over time, and no "monodiet" will contain all the nutrients you need, in exactly the amounts you need them.

At least, having a varied diet increases your chances of getting everything you need, though that is more likely to see you eating more than you need. There is no perfect solution.