The main reason for gaining weight even after taking mirtazapine without eating is that after mirtazapine treatment for depression, it brings sedation and drowsiness resulting in reduced activity. In addition, mirtazapine can also regulate the nervous system causing metabolic effects. The main reason for obesity is that the calorie intake is greater than the calorie consumption for a long time, and mirtazapine has a direct or indirect effect on metabolism by affecting the central nervous system, which not only regulates and controls appetite and hunger. After taking mirtazapine, it affects the nervous system causing hyperphagia. Some people who take mirtazapine do not have hyperphagia because of individual differences. It is also closely related to the dose and the fact that mirtazapine can also affect energy consumption and cause a decrease in energy consumption. Also, after taking mirtazapine, there is often not much energy consumption due to sedation and drowsiness and reduced activity, which can lead to weight gain. By cultivating a healthy lifestyle, we can avoid weight changes after taking mirtazapine. Reasonable and balanced nutrition, scientific and moderate exercise, quitting smoking, limiting alcohol, regular rest, adequate sleep, and psychological balance are very important, and a healthy and enriching lifestyle is also beneficial to the relief of depression.