I tried Adipex a couple of years ago. I was on it for only a couple of months. I lost maybe 15-20 lbs. I had to stop taking it though because it caused me to have seizures. That was the only thing I had been doing different. I was certain it wasn't the Adipex, so a year later I got back on it and the same thing happened...more seizures.
As far as losing weight with Adipex and keeping it off, I didn't keep it off. In fact I gained all that weight back plus some. I hope this info gives you some of the answers you were looking for.