In general, prescription diet pills are
only effective for short-term weight loss. This is true for most
diet drugs such as Phentermine (Adipex, Ionamin), Phendimetrazine
(Bontril) and Diethylpropion (Tenuate) which are all types of
appetite suppressants.
With this in mind, prescription diet pills
can be very effective, leading to an average weight loss of 5
to 22 pounds above that expected with non-drug obesity treatments.
Since people respond differently to different weight-loss medications,
some people may experience more weight loss than others.
Maximum weight loss usually occurs within
6 months of starting treatment. Weight then tends to level off
or increase during the remainder of treatment. Studies suggest
that if a patient does not lose at least 4 pounds over 4 weeks
on a particular medication, then it's unlikely to help the patient
achieve significant weight loss.
Most studies show that the majority of
patients who stop taking weight-loss medications regain the weight
they lost. While this can be attributed to many factors, maintaining
healthy eating and physical activity habits will increase the
chance of keeping the weight off.
How
do I choose? 
