Doctors are proposing a “radical overhaul” of how obesity is diagnosed worldwide amid concerns that a reliance on body mass index may be causing millions of people to be misdiagnosed.
More than 1 billion people are thought to be living with the condition that for decades has been diagnosed by measuring a person’s BMI (their ratio of height to weight) to estimate the amount of excess body fat they have.
However, there are fears BMI on its own is not a “reliable measure” of an individual’s health and may be resulting in both under- and over-diagnosis of obesity, with “negative consequences” for those affected and wider society.
Dozens of the world’s leading experts across a broad range of medical specialisms – including endocrinology, internal medicine, surgery, biology, nutrition and public health – are now calling for a “reframing” of the condition that is causing major harm on every continent and costing countries billions.
Relying only on BMI is “ineffective” because it is not a direct measure of fat, fails to reflect fat distribution around the body, and does not provide information about a person’s health, according to a report published by the experts in the Lancet Diabetes and Endocrinology journal.
The proposed shake-up, endorsed by more than 75 medical organisations around the world, puts forward new ways to diagnose obesity based on other measures of excess body fat in addition to BMI, such as waist-to-hip ratio or waist-to-height ratio, as well as objective signs and symptoms of ill health.
At the moment, some people with excess body fat do not have a BMI that indicates they are living with obesity, meaning potentially serious health problems are going unnoticed and untreated. At the same time, others with a high BMI may be diagnosed with obesity despite maintaining normal organ and bodily functions, with no signs or symptoms of ongoing illness.
Prof Francesco Rubino, the chair of the Lancet commission which produced the report, said the changes would provide an opportunity for health systems globally to adopt a universal, clinically relevant definition of obesity and a more accurate method for its diagnosis.
He said: “The question of whether obesity is a disease is flawed because it presumes an implausible all-or-nothing scenario where obesity is either always a disease or never a disease. Evidence, however, shows a more nuanced reality. 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.
“Considering obesity only as a risk factor, and never a disease, can unfairly deny access to time-sensitive care among 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, with potential harm to the individual and staggering costs for society.”
The experts recommended two new categories of obesity: clinical obesity and pre-clinical obesity.
Clinical obesity would be defined as 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 or eating, as a direct result of excess body fat. Patients with clinical obesity should be considered as having an ongoing chronic disease and receive appropriate management and treatments, such as weight-loss drugs, the experts said.
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Pre-clinical obesity would be defined as obesity with normal organ function. People living with pre-clinical obesity therefore do not have ongoing illness, although they have a variable but generally increased risk of developing clinical obesity and other diseases in the future, including type 2 diabetes, cardiovascular disease, certain types of cancer and mental illness. People in this category should be supported to reduce the risk of potential disease, the experts said.
“Our reframing acknowledges the nuanced reality of obesity and allows for personalised care,” said Rubino, the chair of metabolic and bariatric surgery at King’s College London.
The Royal College of Physicians welcomed the report. Dr Kath McCullough, a special adviser on obesity, said: “For too long, we’ve relied on BMI as a simple measure of obesity, which has often misrepresented the condition and fails to fully reflect how excess body fat impacts a person’s health.
“The commission’s distinction between pre-clinical and clinical obesity represents a vital step forward, highlighting the need to identify and intervene early while providing appropriate care to those already experiencing severe health impacts.”
However, Katharine Jenner, the director of the Obesity Health Alliance, said the priority should be supporting those living with excess weight, “rather than focusing solely on how it is measured”.
