I would be dubious that it has much of an effect long term. People are always looking for some easy way to influence weight loss. Whatever effect it has, I would suspect that it is minor. That said, Dr. Oz did have blinded studies done and there was more weight loss than with placebo, so I guess it works to some extent.
http://www.doctoroz.com/videos...-coffee-bean-projectAs to tolerance, if you can tolerate coffee, you probably can tolerate this supplement. However, if you are taking it in doses higher than you would for a cup of coffee, keep that in mind. Caffeine can increase diarrhea and IBS symptoms. Also be wary if you have glaucoma.
http://www.webmd.com/vitamins-...entName=GREEN+COFFEEJan