Global Commission Proposes ‘Radical’ Overhaul of Obesity Diagnosis

A global expert panel seeks to reframe how obesity is diagnosed by envisioning two levels of disease: a preclinical stage without organ system illness as well as a clinical obesity stage where the organs have been damaged and/or activities of daily living have been impacted.

The panel, made of up 58 commissioners representing multiple medical specialties and countries, concluded that the lack of information on organ function and functional limitations when using body mass index (BMI) and anthropometric measures makes it difficult for clinicians to discriminate between obesity that causes illness and excess adiposity that may coexist with preserved health.

In a press conference held prior to the publication of the commission’s report today in The Lancet Diabetes & Endocrinology, chair Francesco Rubino, MD (King’s College London, England), said the controversy over what constitutes obesity stems primarily from the fact that it exists on a spectrum. The novel preclinical versus clinical obesity framework, he added, prevents a blanket approach that might under- or overdiagnose patients.

”Defining preclinical and clinical obesity informs strategies [at] a clinical level and a policy level,” Rubino said. “So, for preclinical obesity, obviously, you would try to implement risk reduction and use prophylactic interventions, if necessary. In clinical obesity, of course, the therapy has to be timely and corrective or therapeutic, what we define as therapeutic intent.”

Obesity, defined currently as a BMI > 30 kg/m², can incorrectly classify some individuals, including elite athletes, as overweight or obese while excess adiposity can be a sign of other diseases or a side effect of numerous medications, the group notes.

In the paper, Rubino and colleagues acknowledge that the concept of obesity as a disease was a controversial subject even amongst themselves initially, with only one-third of the commissioners supporting the idea that obesity was a stand-alone disease as defined by BMI. Many of them had concerns that up to 40% of people in some countries could be diagnosed as clinically obese overnight if they used that definition, making obesity “a financially and socially intractable issue.”  

Commenting for TCTMD, Andrew J. Sauer, MD (Saint Luke's Mid America Heart Institute, Kansas City, MO), said what the Lancet Diabetes & Endocrinology Commission has done with their reframing of obesity is analogous to what has been seen in other chronic diseases.

“It seems like ancient history, but it wasn't really all that long ago that we talked about heart failure as if everybody had overt heart failure,” he said, noting that this condition is now staged on a spectrum as well. “Now we're [also] going in that same direction, I think appropriately, with cardio-kidney metabolic disease, and in this case, obesity in particular, which makes a lot of sense.”

The reason we were sticking with BMI in the first place is because it's so easy. Michael Blaha

Also commenting for TCTMD, Michael Blaha, MD (Johns Hopkins Medicine, Baltimore, MD) said he views what the commission has done as a step in the right direction.

“The reason we were sticking with BMI in the first place is because it's so easy,” he said. “I imagine that over time, this more mature thinking about obesity, especially among our students and residents, is going to lead to improvements around the way we think about weight and weight management over the lifespan. It'll take a while to filter down, but I'm very anxious to see what percentage of the population really has this [definition of] clinical obesity or preclinical obesity.”

A Radical Change

The Lancet Diabetes & Endocrinology Commission aligns obesity with excessive adiposity, with or without abnormal distribution or function of adipose tissue and with multifactorial causes. This, they say, helps distinguish it from other disorders of adipose tissue that can cause metabolic disease in the absence of obesity.

“We define clinical obesity as a chronic, systemic illness characterized by alterations in the function of tissues, organs, the entire individual, or a combination thereof, due to excess adiposity,” they write, adding that this stand-alone disease can lead to severe end-organ damage, causing life-altering and potentially life-threatening complications.

“We define preclinical obesity as a state of excess adiposity with preserved function of other tissues and organs and a varying, but generally increased, risk of developing clinical obesity and several other noncommunicable diseases (eg, type 2 diabetes, cardiovascular disease, certain types of cancer, and mental disorders),” they add.  The absence of organ dysfunction is the hallmark of this category.

Rubino said while the new definitions constitute “a radical change,” it doesn’t mean BMI is being thrown out completely as a clinical tool.

“We're using BMI and measures of weight distribution as part of the documentation of excess body fat. So, that still plays a role, but it's not the only role here,” added commission member Louise A. Baur, MD (The Children’s Hospital at Westmead, Sydney, Australia).

Defining preclinical and clinical obesity informs strategies [at] a clinical level and a policy level. Francesco Rubino

The group recommends confirming excess fat mass and its distribution with 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; or direct body fat measurement (such as by a bone densitometry scan or DEXA) regardless of BMI. For those with a BMI over 40, no additional documentation is needed.

Sauer noted that much of the 18 diagnostic criteria the commission proposes for clinical obesity in adults—they’ve created 13 separate/overlapping criteria for adolescents and children—correlates with BMI, which may be problematic.

“What I'd like to see for patients at risk for preclinical or clinical obesity [is] gold standard measurements, which would probably be based on imaging,” he said. “Crude bedside measurements just may not be good enough. So, whether we need DEXA or MRI  . . .  I think is an important part of the debate.”

Robert Eckel, MD (University of Colorado Anschutz Medical Campus, Aurora), another commission member, said DEXA and other imaging are not mandated because much of the proposed criteria can be easily obtained from a careful history, including questions about limitations of daily activities, and should not add too much extra work for clinicians or assistants taking histories.

For Blaha, imaging isn’t practical in the diagnosis of obesity, although he said it could be useful in some instances.

While it will be important to determine how the new framework changes population burdens of obesity, Rubino believes the definitions are ready for clinical use.

“We hope that this leads to a change in practice and maybe even before that, [to] change in mindset. When people go to see a doctor today [or] in the past with obesity, they don't necessarily get a full clinical assessment,” he said.  ”If nothing else, [this] will result in more accurate clinical assessment and diagnosis and appropriate treatment if necessary.”

In Line With Emerging Thinking

To TCTMD, Blaha said the new approach puts into practice what many clinicians see every day in their clinics. For others, he said, “there will be a need for education and rethinking of how we teach clinical obesity.”

Another consideration is the GLP-1 receptor agonists, which not only have changed the landscape of obesity treatment over the last few years, but were studied and approved based on BMI considerations.

“If you look at the FDA label for weight-loss therapies it says BMI over 30 or BMI over 27 with an obesity-related risk factor, which is sort of what they're getting at here with fat mass plus the consequences of that fat mass,” Blaha said.  ”So, it's not so different, but there are some people with a BMI above 30 who really shouldn't be diagnosed with clinical obesity, so this could sharpen our focus on who really will benefit from therapy a little bit, especially as we see more benefits of weight loss therapy on other things like the liver, sleep apnea, osteoarthritis, et cetera. These [new definitions] will be quite concordant with evolving thinking on the GLP-1s.”

Sauer added that with less reliance on BMI with its inherent racial and sex biases, the new definitions also could theoretically improve access to weight loss medications for many people.

“We have treatments now that are cardioprotective . . . and we know we need to focus more and more on patients who are at risk or who have preclinical disease rather than waiting until they develop overt disease and then treating when it's harder to reverse the pathophysiology,” he said.