There are three mechanisms of action of diet pills, which mainly play a role by inhibiting people's appetite, promoting the excretion of nutrients and reducing the absorption of nutrients. Diet pills lose weight quickly in a short time, but they still have side effects. The main side effects are: first, the side effects of the drug itself, taking diet pills may cause liver and kidney damage or allergies and other side effects; Second, the nutrition is unbalanced or malnourished. Drugs will reduce the absorption of nutrients while reducing the calories of food, leading to decreased immunity, endocrine disorders and other symptoms; Third, the weight is easy to rebound. Diet pills work by suppressing appetite or promoting excretion. Once the drug is stopped and the diet is resumed, the weight is easy to rebound; Fourth, some illegal weight-loss drugs on the market may be mixed with diuretics or thyroid tablets, which can reduce weight by diuresis or increasing metabolic rate, with greater side effects.