The trouble with diet pills is they don't work long term - the only thing that does is to change your lifestyle. I joined a health club after graduating to shed all those study pounds, only to nearly double my weight when I became pregnant (you're supposed to gain 20-30 pounds to ensure a healthy baby; I wanted a really healthy baby, so I gained eighty.) Took me a year to get the weight back down. A few things I do: walk an hour a day, take stairs rather than escalators when feasible, and drink only water. Soft drinks aren't a part of my life.
I was on an appetite suppressing drug, Strattera, a couple of years ago for ADHD and lost 15 pounds immediately. Trouble was, when I stopped taking it, I was hungrier and more food-obsessed than I'd ever been (except during pregnancy), and ended up overshooting my previous weight before things returned to normal. And I wonder if phentermine does the same thing, considering that people regain the weight when they stop taking it - both drugs increase dopamine in the CNS, though atomoxetine does so mainly in just the prefrontal cortex.