Overweight and obesity are terms that refer to an excess of body fat and they usually relate to increased weight-for-height. The most common method of measuring obesity is the Body Mass Index (BMI).
BMI = Person’s weight (kg) / Person’s height (in metres)².
In adults, a BMI of 25kg/m² to 29.9kg/m² means that person is considered to be overweight, a BMI of 30kg/m² or higher means that person is considered to be obese. A BMI of 40kg/m² or higher means that person is considered to be morbidly obese. The National Institute for Health and Clinical Excellence (NICE) recommends the use of BMI in conjunction with waist circumference as the method of measuring overweight and obesity and determining health risks.
BMI does not distinguish between mass due to body fat and mass due to muscular physique, nor the distribution of fat. In order to measure abdominal obesity, waist circumference is measured, and categorised into desirable, high and very high, by sex-specific thresholds (cm):
- Men: Desirable = Less than 94, High = 94-102, Very high = More than 102
- Women: Desirable = Less than 80, High = 80-88, Very high = More than 88
The main source of the data on overweight and obesity information is the Health Survey for England (HSE), and covers adults aged 16 and over.