A big belly may be caused by physiological factors such as drinking and eating too much alcohol, or pathological factors such as ascites. 1. Physiological factors: Alcohol contains a large amount of sugar, and when drinking too much alcohol, the sugar cannot be metabolized and is converted to fat, which accumulates in the abdomen and leads to the formation of a big belly. Eating too much leads to energy metabolism, which accumulates in the body and turns into fat, forming a big belly. Exercise is reduced, the basic metabolic rate decreases, also easy to gain weight, causing a big belly. 2. Pathological factors: when the patient has cirrhosis of the liver, stomach cancer, liver cancer, resulting in ascites in the abdominal cavity, a big belly will also appear. There may also be other reasons for a big belly, it is recommended to go to the hospital in time, improve the examination to clarify the cause of the disease, and then give targeted treatment or treatment under the guidance of the doctor.