Obesity can lead to a complex range of diseases including diabetes, hypertension, osteoarthritis, certain types of cancer, and heart disease. It is now identified as the second leading preventable cause of death after cigarette smoking. Obesity and overweight occurs due to imbalance between calories consumed and calories utilized. Weight loss drugs, also called anti-obesity medications that help to reduce weight. Obesity drugs may be used in adult patients at medical risk from obesity BMI 30 or greater, or overweight patients with established BMI 27. The ideal anti-obesity drug would produce sustained weight loss with minimal side effects. These drugs alter one of the fundamental processes of the human body, weight regulation, by altering either appetite, or absorption of calories. In past years, numerous drugs have been approved for the treatment of obesity. However, most of them have been withdrawn from the market because of their adverse effects. Hopefully, more effective and better tolerated anti-obesity drugs will be developed through an improved understanding of the multiple mechanisms and complex physiological systems targeting appetite. Key words: Obesity, anti-obesity drugs, weight loss, side effects.