With the improvement of people’s living standards, people’s eating habits have changed a lot. Now obesity has become a worldwide common disease. Therefore it is necessary for us to have some knowledge about obesity. Obesity refers to a certain degree of obvious overweight and fat layer is too thick, is the body fat, especially triglyceride accumulation is too much and lead to a state. As a result of excessive food intake and reduced physical activity, excessive accumulation of body fat leads to excessive weight gain and causes pathological and physiological changes in the human body. Now the scientific assessment of obesity is mainly two indices: First: obesity, obesity = (actual weight – standard weight) ÷ standard weight × 100%. Obesity within ± 10%, called normal and moderate. Obesity over 10% is called overweight. Obesity over 20%-30% is called mild obesity. Obesity degree more than 30%-50%, called moderate obesity. Obesity degree more than 50%, above, called severe obesity. Obesity less than -10%, called thin. Obesity less than -20% above, called wasting. Second: body mass index, is what we often say BMI = weight (kg) / height 2 (m).