Body mass index (BMI) is an index to judge whether a person is obese or not. Its calculation method is body mass index = weight (kg)÷ height 2 (m), such as height 1.6m, weight 5kg, and her body mass index =5÷ 1.6? = 19.5。 The body mass index of Chinese adults is ≤ 18.4, 18.5-23.9 is normal, 24-27.9 is overweight, and ≥28 is obese.