Editorials

Is BMI the best measure of obesity?

BMJ 2018; 360 doi: https://doi.org/10.1136/bmj.k1274 (Published 29 March 2018) Cite this as: BMJ 2018;360:k1274
  1. Peymane Adab, professor of chronic disease epidemiology and public health1,
  2. Miranda Pallan, senior clinical lecturer in public health1,
  3. Peter H Whincup, director2
  1. 1Institute of Applied Health Research, University of Birmingham, Birmingham, UK
  2. 2Population Health Research Institute, St George’s, University of London, London, UK
  1. p.adab{at}bham.ac.uk

It works for most people most of the time

Obesity, defined as abnormal accumulation of fat such that health is impaired,1 is most commonly assessed using the body mass index (BMI). But some people have questioned whether BMI is the best diagnostic measure.

To answer this, we need to consider the objectives of measurement (clinical assessment, surveillance, evaluating response to interventions), the definition of “abnormal” fat accumulation, and the characteristics of a good measurement tool (accuracy and acceptability). Accurate diagnosis of obesity is important, not only for the individual, when misdiagnosis could lead to undertreatment or potential stigma, but also at the population and policy levels. Inaccurate measurements could mislead our interpretation of the epidemiology of obesity or planning of services.

The most accurate direct measures of the amount and distribution of adipose tissue include dual energy x ray absorptiometry (DEXA) and imaging techniques. Increasing total body fat, measured by DEXA, is associated with higher mortality risk.2 However, imaging techniques have shown that fat distribution (specifically visceral fat) is a more important predictor than total fat levels.3 Despite their accuracy, these techniques are cumbersome …

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