Weight loss is a long term process, so one can not expect to receive fast results in the short term.
People who use medications to help them lose weight may not be satisfied with the prescribed dosage and increase it in hopes of better results. This can result in serious bodily injury or even death. However, these medications still remain very popular on the weight-loss market because of the false promises they offer. Claims of losing weight without diet and exercise are just not true, regardless of the type of medication you're taking.

Currently, the medicines on the market are categorized into three types:
The first type are appetite suppressants. They mainly adjust the central nervous system  to suppress the appetite, as to achieve the goal of weight loss. They primarily are Amphetamine and its derivatives, such as Fenfluramine (also known as Pondimin), Amfepramone (also known as Anorex) and so on. Fenfluramine and Amfepramone are psychotropic drugs, which are addicting to long term users.

The second type are metabolism boosters. They are mainly the dietary fiber, which inhibits the break down of gastrointestinal food through the promotion of gastric emptying, and reduce the absorption of energy and nutrient to increase satiety so as to achieve weight loss.

The third type are diuretic or laxative drugs. The diuretics dehydrate the body to lose weight so that the body only loses water but not the fat. Diuretics can also destroy kidney functions. Laxatives produce diarrhea and reduce the appetite. Long term usage of laxatives can cause relaxation of the intestines and other gastrointestinal diseases. Long term usage will disrupt the normal function of the intestinal tract, affecting the absorption of nutrients which can lead to dehydration and electrolyte imbalance in addition to malnutrition, irregular heart rate and health problems.

Long term usage of weight-loss drugs can also cause lethargy, loss of appetite, dizziness, headache, xerostomia, gastrointestinal discomfort, decreased libido, sweating, heart palpitations, anxiety, insomnia and blurred vision. Some of the medicines of weight loss on the market were originally used for the purpose other than weight loss and have different degrees of side effects. So if one takes these medicines, he/she must do so under medical supervision.