What should be the value of BMI for it to be classified as obesity?

BMI stands for the Body Mass Index which is used to predict weight for the respective height. It is defined as the weight in kilograms divided by the square of height in metres and is expressed as kg/m2. A value of BMI > 30 is classified as obesity and a BMI of > 40 is classified under class III obesity. A BMI > 20 up to 30 will include those who are pre-obese and the overweight. Ref: Park's Textbook of Preventive and Social Medicine 19th Edition; Pages 332 - 335; 515.