Well lets consider this logically, lossing weight fast is bad for you. The body metabolises fat and protein. Ketones will appear in your urine (indicator of fat metabolis) and the fat lost will be metabolically active that means your most likely to put it straight back on again.
The areas where you are most likely to loss fat are your stomach and chest, that means your boobs hunny, along with some from your arms and legs. Fundamentally your bottom will be the second last to loss fat and your major muscle groups that is your legs, biceps and thighs wont really feel the effects (although they will before your arse does).
Lossing weight without exercise means protein is metabolised as well and this means you'll lose muscle tone as well. So we've established that quickly lossing weight is bad for you and won't really work. Having said that a stone in 3 - 4 months is perfectally fine. So now then lets look at weight loss pills.
There are many formula's and the most famous turned out to be tapeworm eggs. In theory there are several ways for them to work, raising your metabolisum or lowering your ability to digest it. However I have NO idea how they actually work, in reality. Personally I wouldn't go screwing around with my body without knowing what they do.
Finally there is NO easy way of losing weight, this is because its a selectable trait and we've evolved to conserve weight as much as possible. I would advise against them, and if you want to lose weight do it the old fashioned way it isn't easy but it is the best, good luck.