How we define obesity needs to become more nuanced, a report has argued, with body mass index (BMI) as a measure alone being too simplistic.
The report, by The Lancet Commission on Obesity and published in the journal The Lancet Diabetes and Endocrinology, has argued that the definition of obesity needs to be split in two.
The term “clinical obesity” should be used for patients with a medical condition caused by their weight, while “pre-clinically obese” should be applied to those remaining fat but fit, although at risk of disease, the commission argued.
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Simply relying only on BMI – which measures whether someone is a healthy weight for their height – to determine obesity is too simplistic, the commission has said.
“Current BMI-based measures of obesity can both underestimate and overestimate adiposity and provide inadequate information about health at the individual level,” the commission said.
A commission, organised as a partnership between the medical journal and King’s Health Partners and endorsed by more than 75 medical organisations around the world, has argued a more nuanced approach is needed.
This needs to be one based on other measures of excess body fat in addition to body mass index (BMI), and objective signs and symptoms of ill health at the individual level.
Bariatric surgeon Professor Francesco Rubino, from King’s College London, who chaired the expert group, said: “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.
“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 pre-clinical obesity, who have an increased health risk, but no ongoing illness. This will facilitate a rational allocation of healthcare resources and a fair and medically meaningful prioritisation of available treatment options,” Professor Rubino added.
Whilst recognising BMI is useful as a screening tool to identify people who are potentially living with being overweight, the commission authors recommend moving away from detecting obesity based on BMI alone. Instead, they recommend confirmation of excess fat mass 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 (for example >40kg/m²) excess body fat can be pragmatically assumed.
Clinical obesity in this context should be defined as a condition 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, the commission argued.
People with clinical obesity should be considered as having an ongoing chronic disease and receive appropriate management and treatments. Pre-clinical obesity, by comparison, should be defined as a condition 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 several other non-communicable diseases 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 has recommended.
“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, from the World Health Organization 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,” Galea added.
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