Obesity occurs when the body mass index is 30.0 kg/m2 or greater. Body mass index (BMI) or Quetelet index is a simple way to estimate the percentage of fat in the body. It is calculated by dividing an individual’s weight (in kilograms) by the square of the individual’s height (in meters). For example, a man who weighs 88 kilograms and is 1.7 meters tall has a BMI of:
88 kg ÷ (1.7 m)2 = 30.4 kg/m2.
Compare this BMI with the BMI values in Table below. The man’s BMI is greater than 29.9 kg/m2, so he would be considered obese.
|Weight Status||BMI Value (kg/m2)|
|Underweight||less than 18.4|
|Normal||from 18.5 to 24.9|
|Overweight||from 25 to 29.9|
|Obese||more than 30|
The combination of eating too much and moving too little generally causes obesity. The best way to lose weight and avoid obesity is to eat less and exercise more. However, many factors may play a role in obesity. Several genes have been identified that control appetite and may contribute to some cases of obesity. Also are important the environmental factors such as the availability of high-fat, high-Calorie fast foods and food advertisements.