Fontex and Prozac, which are similar, have documented effects against bulimia. As far as we know, there have been no scientific studies of St. John's Wort in this matter. St John's Wort is used against depression and has been shown to be harmless. It can therefore be obtained without a doctor's prescription, so it is easy to try it.
If it has no effect you can then decide whether you will follow your doctor's advice and at least find out what Fontex can do for your bulimia. It is not until you know your reaction to the drug that you will have a sound foundation for knowing if you want to continue with the drug. Perhaps you will find out that Fontex is not for you or maybe you will benefit greatly from it. You can only find out by trying the drug.
Caution: St John's Wort may reduce the effect of other drugs, including contraceptive pills. In case you use other drugs be sure to consult your physician before you start using St John's Wort. For example it has been known that women who are on the pill and St John's Wort have become pregnant.