Intended for healthcare professionals

Practice ABC of obesity

Assessment of obesity and its clinical implications

BMJ 2006; 333 doi: (Published 28 September 2006) Cite this as: BMJ 2006;333:695
  1. Thang S Han, specialist registrar,
  2. Naveed Sattar,
  3. Mike Lean
  1. 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.

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    For weight measurement subjects should ideally be in light clothing and bare feet, fasting, and with empty bladder; repeat measures are best made at same time of day

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    Levels of health risks associated with waist circumference (cm), defined by waist circumference action levels in white men and women

    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.

    The correlation of visceral fat with waist circumference is strong. Adapted from Han TS et al. Int J Obes Relat Metab Disord 1997;21: 587-93

    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.

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    Classification of body fatness based on body mass index according to World Health Organization


    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 …

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