Weight loss pills or anti-obesity drugs are pharmacologically active substances that control weight or reduce it. These drugs affect one of the most fundamental processes of our body, weight control, by modifying either appetite metabolism or absorption of food. It may be the first drug to eliminate or regulate almost all the complex processes of weight gain and weight loss, without involving any side effects. Weight loss pills work by making the brain think that the body does not need food, and thus the appetite is suppressed. This suppresses the appetite in turn so that the person cannot eat much and consequently will only eat a very small amount.