There are many causes of fatty liver. Simple fatty liver refers to fatty liver in obese people. Half of obese people can have mild fatty liver, while the incidence of fatty liver in heavy obese people can reach 60% to 90%. Therefore, simple fatty liver should have the following characteristics: 1. Overnutrition or familial tendency to obesity, weight more than 10kg above the normal standard. Normal human standard weight = height (cm) – 105 = weight (kg) or the square of weight in kilograms divided by height. 2, no history of heavy alcohol consumption, no history of drugs and other chronic metabolic diseases (such as diabetes), etc. 3.No pathogenic indicators of viral hepatitis (HBVDNA, HCVRNA, etc.) are negative. 4, abnormal liver function, no or worry mild ALT elevation, usually not more than 2 to 4 times the normal value. The latter can become steatohepatitis. 5, serum cholesterol, triglycerides and low-density lipoprotein, most of them have abnormalities; on the contrary, the lipid changes in hepatitis combined with fatty liver are milder than those in simple fatty liver, and can even be normal. 6, ultrasound examination, no evidence of chronic hepatitis damage, only the characteristics of fatty liver, such as liver volume increased, the liver foreground echogenic dense, enhanced density, the posterior field sparse, reduced density, forming a “sonic attenuation” phenomenon. The vascular structure of the liver is not clear, and the ductal structure is blurred and unclear. 7. Liver pathological examination shows hepatic steatosis, and fatty vesicles (McRae’s vesicles) can be seen in the liver tissue.