As early as 1984, WHO listed obesity as a disease, called “obesity”, and now obesity has become one of the three major diseases (smoking, obesity, AIDS) that affect health globally. Successful control of obesity can not only maintain physical and mental health, prolong life expectancy, but also reduce the risk of cardiovascular disease and fatty liver. Obesity refers to the accumulation of too much fatty tissue in the body, clinically, the standard weight, and body mass index as the standard of obesity, the simple formula for calculating the standard weight is: weight (Kg) = [height (cm) – 100] multiplied by 0.9 or weight (Kg) = height (cm) – 105, in general, where the actual weight exceeds 10% of the standard weight can be called overweight, more than 20% is called obese. But overweight can also be due to muscle development or edema, so the diagnosis of obesity to exclude these factors. For many reasons, each person’s weight cannot be exactly the same as the standard weight, therefore, the difference between the actual weight and the standard weight within the range of plus or minus 10% is considered normal. BMI = weight (Kg) divided by (height squared), the unit of height is: meters, according to the data calculated by the body mass index, according to the WHO (World Health Organization) According to the standard, men >27 and women >25 are considered obese. In the case of unexplained mild abnormal liver function, especially simple transaminase elevation, in addition to verification of blood lipids and ultrasound, the body mass index can also be analyzed to determine whether there is a possibility of fatty liver, in order to clarify the cause and targeted treatment.