BMI Alone Can't Diagnose Obesity: New Diagnostic Criteria for 'Clinical Obesity' Proposed

A report by an international expert commission calling for a change in how obesity is diagnosed by body mass index (BMI) alone was published in The Lancet Diabetes & Endocrinology. It was led by Professor Rubino F of King's College London in the United Kingdom, and 58 experts from multiple specialties and countries took part in the consensus process. People with lived experience of obesity were also included as members.

Distinguishing 'clinical obesity' from 'preclinical obesity'

The commission defined a state in which excess fat (adiposity) has reduced the function of organs or tissues, or has substantially limited daily life, as 'clinical obesity,' a chronic disease. By contrast, it classified a state with excess fat but preserved organ function as 'preclinical obesity,' a stage with a high risk of diabetes, cardiovascular disease and other conditions but not yet a disease.

The diagnostic procedure changes as well. BMI would be used only for population-level risk assessment or screening, and for individuals the commission recommended confirming excess fat by direct measurement of body fat or by adding at least one other measure, such as waist circumference, waist-to-hip ratio or waist-to-height ratio. With a BMI above 40, excess fat can be assumed without further confirmation. For clinical obesity, it recommended timely, evidence-based treatment, and for preclinical obesity, counseling and follow-up monitoring. The recommendations were agreed by 90 to 100% of the commissioners and endorsed by 76 organizations.

Application in practice needs validation

The proposal is significant in that it calls for looking at obesity in terms of organ function rather than weight. However, this is an expert consensus document rather than a study presenting new clinical data, and how accurate and practical these criteria are in actual care and in insurance and policy decisions needs separate validation.