Experts Pitch Major Overhaul to How Obesity Is Diagnosed

Medical experts from around the globe proposed a more nuanced approach to diagnosing obesity that does not rely exclusively on body mass index (BMI) alone.

Writing in The Lancet Diabetes & Endocrinology, the global commission argued that to reduce misclassification, other measures of body fat — such as waist circumference or direct fat measurement — should also be used, along with signs and symptoms of ill health at the individual level.

In addition, the group of experts propose two separate categories of obesity: clinical obesity, “a systemic, chronic illness directly and specifically caused by excess adiposity”; and preclinical obesity, “excess adiposity with preserved organ and tissue function, accompanied by an increased risk of progression to clinical obesity or other non-communicable diseases.”

A goal of the commission — which was led by Francesco Rubino, MD, of King’s College London in England, and endorsed by more than 75 medical organizations across the world — was to settle the debate over whether obesity is a disease.

“Our reframing acknowledges the nuanced reality of obesity and allows for personalized care,” Rubino said in a statement. “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. This will facilitate a rational allocation of healthcare resources and a fair and medically meaningful prioritization of available treatment options.”

For example, those with preclinical obesity may be better suited for prophylactic interventions like diet and exercise, while those with clinical obesity may require more time-sensitive therapeutics like drugs and surgery, Rubino said during a press briefing.

Co-author Robert Eckel, MD, of the University of Colorado Anschutz Medical Campus in Aurora, emphasized that what the commission has come up with is “entirely novel.”

“There’s so many unanswered questions that relate to the prevalence and ultimately, what happens to people with preclinical obesity,” he said. “A decade from now, we may know more about this risk gradient for preclinical obesity in terms of whether a more zealous intervention is necessary for some people, but not all. This is a whole new domain of operating clinically and giving patient advice going forward.”

Clinical vs Preclinical Obesity

Clinical obesity — now defined as a state of ongoing illness — is hallmarked by reduced tissue or organ function due to excess adiposity that affects daily activities. This can manifest in ways like breathlessness, knee or hip pain, joint stiffness, reduced range of motion, metabolic dysfunction, and dysfunction of organ systems.

For a diagnosis of clinical obesity under the proposal, individuals must check off two main criteria: confirmation of excess body fat, plus signs of ongoing organ dysfunction and/or age-adjusted mobility limitations or limitations of daily living. The commission listed 18 diagnostic criteria, including limitations of day-to-day activities, as well as those that reflect dysfunction with the following organ systems:

• Central nervous system
• Upper airway
• Respiratory
• General cardiovascular and specifically ventricular, atrial, pulmonary, thrombosis, and arterial cardiovascular
• Metabolism
• Liver
• Renal
• Urinary
• Female and male reproductive systems
• Musculoskeletal
• Lymphatic

When diagnosing children and adolescents with clinical obesity, they have a similar but separate list of 13 diagnostic criteria.

“A diagnosis of clinical obesity should have the same implications as other chronic disease diagnoses. Patients diagnosed with clinical obesity should, therefore, have timely and equitable access to comprehensive care and evidence-based treatments,” the commission authors noted.

On the other hand, preclinical obesity is highly heterogenous and represents a spectrum of risk. While these individuals also have excess body fat, they don’t have ongoing illness as a result. Instead, people with preclinical obesity can still complete their normal day-to-day activities with no or only mild evidence of organ or tissue dysfunction. However, they are generally at higher risk for diseases like clinical obesity, cardiovascular disease, type 2 diabetes, and some cancers, among other illnesses.

“Preclinical obesity is different to metabolically healthy obesity because it is defined by the preserved function of all organs potentially affected by obesity, not only those involved in metabolic regulation,” the authors pointed out.

Shifting Beyond BMI

To confirm the clinical obesity diagnosis in those with excess body fat, healthcare providers should evaluate the patient’s medical history and conduct a physical examination, standard laboratory tests, and additional diagnostic tests if appropriate during clinical assessments.

While BMI still holds clinical utility, it can over- and underestimate body fat, the authors pointed out, so they propose that clinicians verify obesity status with at least one additional anthropometric measure: like waist circumference, waist-to-hip ratio, or waist-to-height ratio — or direct fat mass measurement by dual-energy x-ray absorptiometry (DEXA) or bioimpedance.

“[During the exam], we see if there are any signs or symptoms that trigger the suspicion of an organ dysfunction. If there is an organ dysfunction and it’s clear, there it is, clinical obesity. If there’s organ dysfunction that is not completely clear, you escalate the diagnostic as needed,” Rubino said. “This is … the job description of any clinician from primary care all the way to specialists.”

These additional body measurements aren’t necessary in patients with a BMI over 40, Eckel pointed out, who said excess body fat can be assumed in someone with this high of a BMI.

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