- Thang S Han, specialist registrar,
- Naveed Sattar,
- Mike Lean
- department of diabetes and endocrinology, University College London Hospitals.
Obesity can be assessed in several ways. Each method has advantages and disadvantages, and the appropriateness and scientific acceptability of each method will depend on the situation.
The assessment methods often measure different aspects of obesity—for example, total or regional adiposity. They also produce different results when they are used to estimate morbidity and mortality. When there is increased body fat, there will also be necessary increases in some lean tissue, including the fibrous and vascular tissues in adipose tissue, heart muscle, bone mass, and truncal or postural musculature. All these non-fat tissues have a higher density (1.0 g/ml) than fat (0.7 g/ml). The density of non-fat tissues is also increased by physical activity, which of course tends to reduce body fat.
In general, measurements of body weight and body dimensions (anthropometry) are used to reflect body fat in large (epidemiological) studies or in clinic settings as such measurements provide a rapid and cheap way to estimate body fatness and fat distribution. Densitometry or imaging techniques are used in smaller scale studies such as clinical trials.
Body mass index (BMI) has traditionally been used to identify individuals who are the most likely to be overweight or obese. It is calculated by dividing the weight (in kilograms) by the height …