Is obesity a disease? And if so, how do we diagnose it?

The Lancet Commission on Diagnostic Criteria of Clinical Obesity is now running, hosted by King’s Health Partners Diabetes, Endocrinology and Obesity.   Diabetes

The Lancet Commission on Diagnostic Criteria of Clinical Obesity aims to define criteria that discriminate between the condition of obesity (a risk factor for other diseases) and clinical obesity - intended as a disease state. This would be associated with distinct pathophysiology and specific signs and symptoms that reflect ongoing illness.

This Commission is organised as a partnership between the medical journal The Lancet Diabetes & Endocrinology and King’s Health Partners (KHP) Diabetes, Endocrinology and Obesity. 

The Commission is led by a steering group of leading international experts, chaired by Prof Francesco Rubino, Chair of Metabolic and Bariatric Surgery in the Faculty of Life Sciences and Medicine, King's College London, and Honorary Consultant at King's College Hospital NHS Foundation Trust.

The notion that obesity is not merely a risk factor for various illnesses, such as diabetes, but a disease in its own right, has been proposed by several organisations. These include medical societies, the WHO, the European Commission, and the USA’s Institute of Medicine among others. The idea of obesity as a stand-alone disease entity, however, remains highly controversial, both within and beyond medical circles.

Recognising obesity as a disease would acknowledge the fact that many people with obesity objectively suffer from ongoing illness, provide stronger medical and cultural legitimacy to the condition, increase access to care for those in need, and reduce societal stigma.

However, if obesity continues to be defined only by body mass index (BMI), as it is today, a formal recognition of obesity as a disease poses an objective risk of overdiagnosis, with potentially negative ramifications at clinical, societal, and political levels.

The report from this Lancet Commission aims to inform clinical decision-making, insurance coverage of evidence-based treatments, and more effective public health interventions to tackle the obesity epidemic, globally.

Lancet Commissions bring together leading international experts with a broad range of expertise to address the most pressing issues in global health and clinical medicine. Commissions are science-led inquiries aimed at achieving transformational change, and they are especially focused on policy or political action. 

The Lancet Commission on Diagnostic Criteria of Clinical Obesity engages a group of around 60 international experts selected by members of the steering committee in collaboration with Editors of Lancet journals. Commissioners include academic clinicians specialised in obesity care and non-clinical professionals with track records of contribution to the understanding of mechanisms responsible for the clinical manifestations of obesity.

Given the global nature of the problem, Commissioners have been selected to represent various scientific disciplines and different healthcare systems from around the world. Commissioners participate in a series of online meetings (approximately every six-eight weeks) as well as offline activities to discuss scientific evidence and develop consensus among the group.

Prof Francesco Rubino said:

For many years the medical community has conceptualised obesity as a modifiable risk factor. Accordingly, we have created a shared narrative of obesity that focuses on the risk for future complications and other diseases.
Even as we realised that obesity can be a disease in and by itself, at least in some patients, we have not changed the narrative and we have not yet provided evidence-based criteria for its diagnosis. 
This has many negative ramifications. On the one hand, a blanket definition of obesity as a disease would overdiagnose the problem, making it an intractable problem for policy makers. On the other one hand, the lack of recognition of obesity as a disease is inconsistent with current scientific knowledge. It misleads clinical decision-making and public health strategies, contributes to stigma and leaves patients vulnerable to significant harm, as quackery and marketing of unproven remedies go unchallenged.
KHP Diabetes, Endocrinology and Obesity is quickly becoming a major UK centre for diabetes and obesity research. As host for the Commission, we are building on our rich history and world-leading clinical academic strengths to improve the lives of our patients and address the inequalities gap within the diverse communities we serve.
We believe that developing a diagnostic criteria of clinical obesity fits with the KHP objectives to improve the lives of people living with obesity and address the inequalities gap both at local and global level.
The challenge facing this Lancet Commission is to define scientifically sound, pragmatic criteria for the diagnosis of clinical obesity so that we can tackle the obesity epidemic globally. I am excited that this process is well underway and look forward to working with colleagues across the world.

The report from the Commission will be announced at a dedicated event and published in a future issue of The Lancet Diabetes & Endocrinology. Previously published Lancet Commissions can be viewed at