Imma Perfetto
Cosmos science journalist
The way clinicians diagnose obesity is set to change with new guidelines acknowledging that some obese people are perfectly healthy, while others live with chronic disease.
“Obesity is a spectrum,” says Professor Francesco Rubino from the UK, who chaired the Commission that developed the guidelines. “You can have people who have excess body fat but have preserved, normal organ function, and can go about their lives for quite some time in a normal way, sometimes even for a lifetime.”
A group of 58 international experts developed the new medical guidelines to reflect the nuanced reality of obesity and to enable evidence-based, personalised approaches to its prevention, management, and treatment.
They published the new Global Commission on Clinical Obesity in The Lancet Diabetes & Endocrinology. It sets out a more clinically relevant definition of obesity and an accurate method for diagnosing when it is a chronic disease.
“We want to overhaul, dramatically, the ideas about how we diagnose obesity and how we improve global health care practices,” saysJohn Dixon, Adjunct Professor at the Iverson Health Innovation Research Institute at Swinburne University of Technology, Australia.
“The aim is to facilitate individualised assessment and care of people with obesity … to deliver the right services to the right people.”
A new way to define obesity
A clinical diagnosis for obesity hasn’t existed before. Instead, obesity has been defined as a body mass index (BMI) of greater than 30Kg/m2 in people of European descent, with different country-specific BMI used to account for ethnic variability of obesity-related risk.
But according to Rubino, chair of metabolic and bariatric surgery at Kings College London in the UK, BMI only takes into account body weight and the height of an individual.
“It doesn’t compute the body composition … [it] doesn’t tell us how well our organs are working, if they’re still normal or they’re dysfunctional, and therefore whether there is health or illness at the individual level.”
The Commission’s new diagnostic criteria recommends that excess body fat be confirmed by either direct measurement, or with BMI and at least one other measurement of body size – waist circumference, waist-to-hip ratio, or waist-to-height ratio.
“There are people who have excess body fat, and not because of other diseases that are associated with obesity, but because of excess body fat itself, they experience impairment in the functions of their organs – the heart, the joints, the kidneys, the liver and so on – so that they have the typical manifestations of an ongoing illness.”
Due to obesity’s effect on mobility, they may also experience substantial limitations to their daily activities.
The Commission has introduced 2 new categories – preclinical obesity and clinical obesity – to reflect the spectrum of obesity.
Once a clinician has confirmed their patient has excess body fat, further assessment – including medical history, physical examination, and standard blood tests – is needed to establish a diagnosis of clinical obesity. This assessment is based on 18 criteria in adults, and 13 in children and adolescents, which relate to multiple organ systems.
Allowing for personalised care for obesity
By distinguishing whether a patient is living with preclinical or clinical obesity, clinicians can tailor the level of intervention to the urgency of care required.
For instance, managing preclinical obesity may focus on risk reduction and preventing a progression to clinical obesity or other obesity-related diseases. This could include evidence-based health counselling for weight loss or to prevent weight gain and health monitoring over time. For those at higher risk – based on family history or a concentration of excess fat around the abdomen, for example – active weight loss interventions may also be appropriate.
“If somebody has already developed clinical obesity, that person has a disease here and now … and it would be inappropriate if we were using preventative or prophylactic interventions to treat an ongoing disease,” says Rubino.
“In this case, you need timely interventions with therapeutic intent aimed at correcting the clinical manifestations.”
Determining the success of treatments should be assessed according to improvement of the signs and symptoms of organ dysfunction, rather than by measures of weight loss.
Louise Baur, professor of child and adolescent health at The University of Sydney and immediate past-president of the World Obesity Federation, says the new diagnostic model allows for standardisation across the global health system.
“The whole idea here is that this should be able to work in low-and middle-income countries, as well as in highly resourced high-income countries,” says Baur.
She says the approach also reduces the influence of age, gender and ethnicity on diagnosis and treatment decisions for obesity.
“The concept allows patient tailored treatment strategies such as risk reduction, particularly in those with pre-clinical obesity, versus therapeutic intent for more intensive treatment in those with clinical obesity, and it allows us to have a medically meaningful and ethical treatment prioritisation and resource allocation.”
