The reason women can’t lose weight is because they are looking for trick, like the south beach diet.
There are no tricks. None. You lose weight by consuming less calories than you burn. That is it.
If your diet does that, you will lose weight. If it does not, you won’t.
When you go off the diet, you obviously gain back all the weight. You need to make lifestyle changes that result in permanently taking in only the amount you burn.