"i am not obese, just about 20 lbs overweight. my problem with weight loss is not really what i&#039;m eating but how much i eat and a lack of motivation to exercise. side effects of phentermine you feel like you are on a constant adrenaline rush and will want to do everything! i advise starting off with phentermine on the weekend to see how you react to it, rather than on a workday. i only take half a pill, and it&#039;s pretty powerful. also you will be thirsty all the time, so drink lots of water. you will lose weight very fast, because you won&#039;t really eat, and will be running around. remember: this is not a magic weight loss pill. you use phentermine as a stepping stone to change your habits. if not, all the weight will come back once you stop."