A vast number of people are overweight. Many of these people are overweight for one simple reason: their lifestyle. A lack of exercise and a carefree diet are main contributors to their obesity. Ridding themselves of burdon of extra weight isn't completely easy. It is as much mental as it is physical. Changing your eating habits and getting into a routine of exercise will generally take care of extra weight in a reasonable amount of time.
For others, however, this is not case. Some have genetic problems while others have emotional problems. This alone results in a vicious cycle of eating to feel better, gaining weight, feeling bad about it, and then eating to get rid of that bad feeling.
For those in this position there is an answer. After a concerted effort to lose weight by traditional means fails... there is drug therapy. Drug therapy isn't answer by itself.