Any expert in this field will confirm that the trick is not how to lose the pounds, but how to prevent them from coming back. Any expert will also confirm that the quicker you lose pounds, the quicker they normally come back.
So all-in-all, I think those commercial diets are overall a bad idea. Good to make the wallet of the author gain some pounds.
Now you must also be careful with wanting to be thin. Many people, girls in particular, are often stressed up over the "wasp waist" shape of the sexy models, and of the girls who pose naked in "dirty magazines". Some people who think who are too fat are actually too thin. One should never try to manipulate their weight for beauty reasons. Only do so when your weight is actually going to threaten your health and both being too fat or too thin can do that.
In the end your weight is decided by many factors, and food is only one of them. Exercise either if the form of sports or by doing loads of physical work, also plays a role. Also note that muscles are heavier than fat, so if you lift a lot of weight and become stronger you might gain a few pounds in the process, but those pounds can be good for you... pounds alone tell only part of the story. Also factors you cannot fully influence play an important role, like stress, diseases and such. And yes, it's always deemed a lame excuse, but some people are heavier and bigger than others due to natural causes and they are not necessarily too fat. Of course, the rub is to sort out for whom that is true and for whom it's only an excuse.
I don't like the idea of experimenting with commercial diets. I think when my weight is really becoming an issue I can better talk with professionals to set out a proper way to go. Sometimes the way to go is very trivial and even downright easy, but sometimes the way is very complicated. What is true for you is hard (if not impossible) to find out when you don't have enough medical knowledge, and weight issues is within medical science a form of science on its own.
The bottom line is, diets in magazines or in bookstores can mostly best be ignored.