Reframing the diagnosis and treatment of obesity

A global Commission of medical experts is advocating for a thorough overhaul of the way obesity is currently assessed — with a particular call to dispense with body mass index (BMI) as a single diagnostic measure.

The Commission on Clinical Obesity has been published in The Lancet Diabetes & Endocrinology and endorsed by more than 75 medical organisations around the world.¹ By advocating for a more nuanced approach, it aims to address limitations in the traditional definition and diagnosis of obesity, which, it says, hinder clinical practice and healthcare policies, resulting in people with obesity not receiving the care they need.

By putting forward a medically coherent framework for disease diagnosis, the Commission also wants to settle an ongoing dispute over the idea of obesity as a disease — one of most controversial and polarising debates in modern medicine.

Commission Chair Professor Francesco Rubino, from King’s College London, said that the question of whether obesity is a disease is flawed, because it presumes an all-or-nothing scenario where obesity is either always a disease or never a disease. “Evidence, however, shows a more nuanced reality,” Rubino explained. “Some individuals with obesity can maintain normal organs’ function and overall health, even long term, whereas others display signs and symptoms of severe illness here and now.”

Rubino said that if obesity is viewed purely as a risk factor, and never a disease, this can unfairly deny access to time-sensitive care for people who are experiencing ill health due to obesity alone. On the other hand, a blanket definition of obesity as a disease can result in overdiagnosis and unwarranted use of medications and surgical procedures.

“Our reframing acknowledges the nuanced reality of obesity and allows for personalised care. This includes timely access to evidence-based treatments for individuals with clinical obesity, as appropriate for people suffering from a chronic disease, as well as risk-reduction management strategies for those with preclinical obesity, who have an increased health risk but no ongoing illness,” Rubino said.

Beyond BMI

Although BMI is useful for identifying individuals at increased risk of health issues, the Commission emphasises that BMI is not a direct measure of fat, does not reflect its distribution around the body, and does not provide information about health and illness at the individual level.

“Relying on BMI alone to diagnose obesity is problematic as some people tend to store excess fat at the waist or in and around their organs, such as the liver, the heart or the muscles, and this is associated with a higher health risk compared to when excess fat is stored just beneath the skin in the arms, legs or in other body areas,” said Commissioner Professor Robert Eckel, from the University of Colorado Anschutz Medical Campus.

“But people with excess body fat do not always have a BMI that indicates they are living with obesity, meaning their health problems can go unnoticed. Additionally, some people have a high BMI and high body fat but maintain normal organ and body functions, with no signs or symptoms of ongoing illness.”

Other diagnostic measures

While acknowledging that BMI is useful as a screening tool to identify people who are potentially living with obesity, the authors recommend moving away from an assessment based on BMI alone. Instead, they recommend confirmation of excess fat mass (obesity) and its distribution around the body using one of the following methods:

• At least one measurement of body size (waist circumference, waist-to-hip ratio or waist-to-height ratio) in addition to BMI.
• At least two measurements of body size (waist circumference, waist-to-hip ratio or waist-to-height ratio) regardless of BMI.
• Direct body fat measurement (such as by a bone densitometry scan or DEXA) regardless of BMI.
• In people with very high BMI (eg, >40 kg/m²), excess body fat can be pragmatically assumed.

Two new categories

The Commission has suggested two categories for disease diagnosis in obesity: clinical obesity and preclinical obesity.

Clinical obesity is defined as a condition of obesity associated with objective signs and/or symptoms of reduced organ function or significantly reduced ability to conduct standard day-to-day activities, such as bathing, dressing, eating and continence, directly due to excess body fat. People with clinical obesity should be considered as having an ongoing chronic disease and receive appropriate management and treatments.

Preclinical obesity is a condition of obesity with normal organ function. People living with preclinical obesity therefore do not have ongoing illness, although they have a variable but generally increased risk of developing clinical obesity and several other non-communicable diseases (NCDs) in the future, including type 2 diabetes, cardiovascular disease, certain types of cancer and mental illness, among others. As such, they should be supported to reduce the risk of potential disease.

“The Commission’s new diagnostic criteria fill a gap in the notion of obesity diagnoses as they enable clinicians to differentiate between health and illness at the individual level,” said Commissioner Dr Gauden Galea, WHO Regional Office for Europe.

“We hope that the broad endorsement of the new framework and diagnosis of obesity by many important scientific societies from around the world will ensure that a systematic clinical assessment of obesity becomes a requirement in health systems globally.”

A need for personalised care

The Commission emphasised that all people living with obesity should receive timely, evidence-based care in line their individual needs.

For example, people with clinical obesity should be helped to fully regain or improve body functions reduced by excess body fat, rather than simply being encouraged to lose weight. Further, the type of treatment and management for clinical obesity — lifestyle, medication, surgery, etc — should be informed by individual risk-benefit assessments and active communication with the patient.

Given people living with preclinical obesity are at risk for future diseases but do not have ongoing health complications, their care should focus on risk reduction. This may range from health counselling and monitoring over time, to more active treatment if needed to reduce high levels of risk.

“This nuanced approach to obesity will enable evidence-based and personalised approaches to prevention, management and treatment in adults and children living with obesity, allowing them to receive more appropriate care, proportional to their needs. This will also save healthcare resources by reducing the rate of overdiagnosis and unnecessary treatment,” said Commissioner Professor Louise Baur, from The University of Sydney.

The Commission involved 56 experts across a broad range of medical specialties, including endocrinology, internal medicine, surgery, biology, nutrition and public health, representing many countries and diverse healthcare systems. The Commission also included people living with obesity and specifically considered the potential impact of the new definitions of obesity on widespread societal stigma.

To read the full Commission, visit https://www.thelancet.com/commissions/clinical-obesity.

_{1. For a full list of medical organisations endorsing the Commission, see appendix 2 (pp 2–3).}

Image courtesy of the World Obesity Federation.