Experts Debate Best Way to Define Obesity
The role of body mass index (BMI) in defining obesity and the definition of obesity as a disease merit reevaluation to avoid unintended consequences, experts said in three new opinion papers. The three statements were all published on July 22, 2src24, in the Annals of Internal Medicine. In one, the authors expressed caution about the
The role of body mass index (BMI) in defining obesity and the definition of obesity as a disease merit reevaluation to avoid unintended consequences, experts said in three new opinion papers.
The three statements were all published on July 22, 2src24, in the Annals of Internal Medicine. In one, the authors expressed caution about the recent movement away from using BMI alone to define obesity, noting that the measure remains a useful population-level and clinical tool for addressing adiposity, particularly within racial and ethnic groups. But the authors of a second paper pointed out that the use of lower BMI cutoffs to define obesity in Asian populations, in place since 2srcsrc4, is inadequate in part because it doesn’t account for heterogeneity among different Asian groups.
And in the third paper, an editorial, an Annals editor cautioned that the recent framing of obesity exclusively as a “disease” rather than a “broader, more inclusive construct” may inadvertently reinforce the bias it was meant to combat.
Asked to comment on the issues raised in the papers, Professor Gijs Goossens of Maastricht University Medical Center, Maastricht, the Netherlands, told Medscape Medical News, “It is important to emphasize that the management and treatment of obesity have wider objectives than weight loss alone and include the prevention, resolution, or improvement of obesity-related complications; achieving better quality of life and mental well-being; and improvement of physical and social functioning.”
Added Goossens, who was an author of a recent European Association for the Study of Obesity (EASO) framework calling for moving beyond BMI in defining obesity, “Personalized therapeutic goals should be set at the beginning of the treatment, according to the stage of obesity, taking into account available therapeutic options, possible side effects or risks, and patient preferences. The drivers of obesity and possible barriers to treatment should also be discussed with the patient.” Goossens emphasized that he was providing his personal views and not speaking for the EASO or his coauthors.
BMI: ‘Not a Perfect Measure of Adiposity but Remains Useful’
In their “Ideas and Opinions” paper, Adolfo G. Cuevas, PhD, of New York University School of Global Public Health, New York City, and Walter C. Willett, MD, DrPH, of Harvard T.H. Chan School of Public Health, Boston, argued that “BMI, although not a perfect measure of adiposity, remains a useful population-level and clinical tool for addressing adiposity, including within groups defined by race and ethnicity.”
They added that despite the criticism that BMI doesn’t distinguish between fat and lean body mass, the measure still strongly correlates with fat mass as well as cardiovascular risk and mortality, and it does so similarly across racial and ethnic groups.
Clinically, Cuevas and Willett pointed out that BMI correlates fat mass as assessed with the gold standard measure dual x-ray absorptiometry but is far simpler and less expensive. Measuring waist circumference can provide additional information about visceral fat and disease risk but is “more difficult to standardize and suffers from the same limitations as BMI when cut points are used.”
They suggest the addition of change in weight since early adulthood and over time as a “simple and sensitive variable” for assessing adiposity.
Luca Busetto, MD, associate professor of medicine at the University of Padua, Padua, Italy, and the first author of the EASO framework, told Medscape Medical News, “The paper from Cuevas and Willet sounds like a strong defense of BMI, and I can substantially agree with this defense…We remain anchored on BMI, but we tried to move beyond it adding an estimate of high risk abdominal fat — waist to height ratio — and coupling the anthropometric assessment with a complete clinical evaluation and staging.”
Goossens commented, “I agree with the authors that despite the limitations of BMI as a measure of body fatness, it remains a useful clinical screening tool. Yet the diagnosis of obesity should not be based solely on BMI” due to the stronger association of abdominal fat with cardiometabolic complications.
That link, he noted, “also applies to individuals with a BMI level below the current cutoff values for obesity, who may already have medical, functional, or psychological impairments. We should be aware of the risk of undertreatment in this particular group of patients.”
Does Calling Obesity a ‘Disease’ Have Unintended Consequences?
In her editorial, Christina C. Wee, MD, senior deputy editor, Annals of Internal Medicine, wrote, “Beyond diagnostic challenges, framing obesity exclusively as a disease rather than a broader, more inclusive construct may have unintended consequences — including reinforcing the weight bias this framing was in part intended to combat.”
Focusing solely on biological causes of obesity while ignoring psychosocial, cultural, environmental, and behavioral contexts could undermine public health and policy efforts to address those factors, Wee argued.
Moreover, she wrote, “Ironically, framing obesity as a disease to justify coverage for treatment reinforces weight bias. It conflates the need to label a condition a disease with healthcare reimbursement and raises the stakes for developing accurate diagnostic criteria…By exclusively linking obesity as a disease to reimbursement, it sends the message that only those who manifest disease from excess adiposity warrant treatment — and, by inference, those on the continuum who have not yet manifested disease do not warrant treatment.”
Likening obesity to other risk factors such as hypertension or dyslipidemia for which treatment is typically reimbursed, Wee pointed out that Medicare still prohibits coverage of medications for obesity.
Regarding the high costs of newer obesity medications and the need for payers and clinicians to ration their use, Wee argued, “Rather than focusing on whether one’s adiposity conforms to an expert panel’s definition of ‘disease,’ we should address how to best stage obesity risk with sufficient accuracy and fairness and reach a consensus on how to prioritize and match treatments to individual patients.”
Busetto said that EASO stands by its definition of obesity as a disease, adding “we can adhere to the suggestion of a holistic approach deciding treatment modalities according to the risk and the presence of mental, functional, and medical complications of impairments. Of course, we cannot agree on any proposal that is oriented at leaving patients with obesity still in the asymptomatic phase of the disease without treatment. This would be like treating diabetes only after the occurrence of nephropathy or managing hypertension only after a stroke. Prevention of the symptomatic stage is a part of obesity management, even beyond weight loss.”
Goossens said, “indeed, it is of utmost importance to develop accurate risk stratification tools for adequately clinical staging of obesity, according to the severity of its medical, psychological and functional impairments.”
Do the Current Lower BMI Cutoffs for Defining Obesity in Asian People Make Sense?
Simar S. Bajaj, AB, of Harvard University, Cambridge, Massachusetts, and colleagues, all of Harvard Medical School, Boston, raised several concerns regarding the 2srcsrc4 World Health Organization’s suggestion to use lower BMI categories for defining overweight and obesity in Asian populations, that is, 23-27.5 kg/m2 and 27.5 kg/m2 or higher for obesity, respectively, as opposed to 25-29.9 and ≥ 3src, respectively, for other populations.
Different Asian countries have created their own obesity BMI cutoffs, ranging from 25 kg/m2 in India to 28 kg/m2 in China. But “Asian Americans continue to be treated as a monolith without official disaggregated cutoffs,” Bajaj and colleagues noted.
The heterogeneity translates to different risk levels across Asian subgroups. For example, in one study, age- and sex-adjusted BMI cutoffs for increased risk of developing type 2 diabetes were 23.9 kg/m2 in South Asian populations, 26.6 kg/m2 in Arab populations, 26.9 kg/m2 in Chinese populations, and 28.1 kg/m2 in Black populations.
These findings raise important questions, Bajaj and colleagues said. “Does it make sense for people of Chinese descent to use the same BMI threshold as the South Asian group when their ‘equivalent risk cutoff’ is closer to that of Arab and Black groups who share the standard BMI threshold?” Most data in this area are cross-sectional rather than the longitudinal data needed to answer those questions, they noted.
They suggest that professional diabetes and obesity organizations consider BMI thresholds to be “placeholders” until more sensitive and specific thresholds can be defined for Asian American populations.
Bajaj and colleagues also noted the need for disaggregated data is not unique to Asian groups but that they focused on Asian Americans for two main reasons. “First, success would create a precedent for complete disaggregation and help ensure that other groups do not stall at an intermediary level. Second, substantial research into Asian ethnic groups — and the WHO’s precedent 2src years ago — creates a solid foundation to build upon.”
Ultimately, they said, “advancing equity will require funding research that engages diverse Asian communities and developing tailored interventions for all ethnicities.”
Cuevas, Willett, Bajaj, and Wee had no disclosures. Goossens received research funding from the European Foundation for the Study of Diabetes, the Dutch Diabetes Research Foundation, and the Dutch Research Council. Busetto received personal funding from Novo Nordisk, Boehringer Ingelheim, Eli Lilly, Pfizer, and Bruno Farmaceutici as a member of advisory boards and from Rhythm Pharmaceuticals and Pronokal as a speaker.
Miriam E. Tucker is a freelance journalist based in the Washington, DC, area. She is a regular contributor to Medscape Medical News, with other work appearing in the Washington Post, NPR’s Shots blog, and Diatribe. She is on X: @MiriamETucker.
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