Appetite Suppression

Appetite is controlled by many factors. Processes in the body tell people when they are hungry and when they are satiated (full). Neurotransmitters (chemical messengers in the brain) such as norepinephrine, serotonin, and dopamine tell the brain that the stomach feels full. Drugs that increase the levels of these neurotransmitters cause a decrease in appetite by relaying the message that the stomach is full, thus telling the brain to send a “stop eating!” signal. These drugs are effective because, in general, appetite decreases when a person feels full. Drugs that increase more than one of the neurotransmitters may be more effective for weight loss than those that increase only one. Some drugs that work in this way also have the effect of increasing the number of calories burned (thermogenesis).

Dopamine, norepinephrine, and serotonin have other responsibilities in the body besides dictating hunger. For example, norepinephrine also helps control blood pressure. Drugs that affect the level of these neurotransmitters interfere with other body processes and produce negative side effects. A drug that increases norepinephrine will decrease appetite, butwill also increase blood pressure. Other common side effects of drugs that increase norepinephrine are dry mouth, insomnia, and constipation. Examples of diet pills that affect these neurotransmitters are sibutramine (Meridia®) and phentermine. Appetite is controlled by many body processes, as shown here. The arrows indicate things that increase and decrease
hunger. All of these processes work by sending signals to the brain to indicate a feeling of hunger or satiety (fullness). Certain diet pills called appetite suppressants may work in the same way as some of these body processes, by sending signals to the brain that indicate satiety and say “stop eating!”