Obesity was initially thought to be a pathophysiological state, but as research on obesity has advanced, it has been found that obesity can induce a variety of diseases, such as hypertension, dyslipidemia, type 2 diabetes, coronary heart disease, sleep apnea syndrome, and certain cancers, and likewise, obesity contributes to the risk of death from these diseases. Thus, the current academic view is that obesity is a chronic disease caused by a combination of genetic and environmental effects, and that this pathophysiological process may lead to an increase in adipose tissue and ultimately to an increase in mortality. The diagnosis of obesity relies mainly on body mass index (BMI), calculated as BMI = weight (kg)/height (m) squared. In China, the reference standard for BMI classification is: BMI <18.5 is malnutrition, BMI of 18.5~23.9 is normal, BMI ≥24 is overweight, BMI of 24~26.9 is obese, BMI of 27~29.9 is obese, BMI ≥30 is severe obesity, and BMI ≥40 is very severe obesity. Moreover, as BMI rises, the risk of suffering from related diseases also increases relatively. In addition to relying on BMI to determine obesity, the waist to height ratio WtHR can also be used to identify central obesity in a simple way. The combined screening of BMI and WtHR can quickly and accurately determine the status of obesity, intervene and treat it early, and effectively reduce the occurrence of related diseases.