Diagnosing and defining obesity

One billion children and adults have obesity.1 Getting the diagnosis of obesity right matters for people and for healthcare systems, particularly when considering prescription of expensive obesity drugs.2 The concept of obesity as excess body fat accumulation may be straightforward,13 but its diagnosis is not.

Body mass index (BMI) has been widely used for clinical diagnosis, but cut-off points for BMI can both underestimate and overestimate adiposity and might poorly identify health risk at the individual level.3 Regardless of how adiposity is measured, it is unclear what can be defined as “abnormal” and “normal.” In the quest to prevent illness, the medical community may choose ever lower thresholds, but in doing so, society is medicalising problems rather than tackling the underlying societal causes of illness.4

The latest attempt to define obesity is from the Lancet Diabetes and Endocrinology Commission, a group of 58 international experts selected to have global reach and differing clinical expertise.35 Consensus was achieved through monthly online evidence presentations and a Delphi process. Many of the commissioners declare funding from or other relationships with drug companies. Scientific or medical bodies and patient organisations were asked to endorse (but could not alter) the guidance, with 76 bodies endorsing …