In the midst of the growing interest in Ozempic and similar weight-loss medications, a group of 58 researchers is questioning the current definition and diagnosis of obesity, arguing that existing methods do not adequately capture the complexity of the condition. They propose a more nuanced approach.
The revised definition from the group, published in The Lancet Diabetes & Endocrinology on January 14, focuses on how excess body fat, referred to as adiposity, impacts the body, rather than solely relying on body mass index (BMI) which relates a person’s weight to their height. They suggest two categories: preclinical obesity, where a person has extra body fat but their organs function normally, and clinical obesity, where excess fat damages the body’s organs and tissues.
Elisabeth van Rossum, an endocrinologist at the Erasmus University Medical Center in Rotterdam, Netherlands, believes this shift could enhance clinical care, public-health policies, and societal views on obesity.
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“Currently, the prevailing idea is to eat less, move more, and you’ll lose weight,” says van Rossum, who was not part of the research. While a healthy lifestyle is crucial, she adds, “if it were that simple, we wouldn’t have an epidemic, and this paper makes a valuable contribution to the conversation about the complexity of obesity”.
Global issue
Over 1 billion people globally live with obesity, and it is associated with about 5 million deaths annually due to conditions like diabetes and cardiovascular disease.
BMI has traditionally been used as a diagnostic tool for obesity because it is easy to measure and compare. However, it does not provide a complete picture of a person’s health as it does not consider differences in body composition, such as muscle versus fat.
For individuals of European descent, obesity is generally defined by a BMI of 30 or higher, which corresponds to a high level of body fat. Nevertheless, a muscular athlete might be classified as obese based on BMI, while an individual with a ‘normal’ BMI may have excess fat increasing their risk of heart issues or other serious health problems, notes Francesco Rubino, a bariatric surgeon at King’s College London. He led the group proposing the new approach.
Rubino and his team suggest a diagnostic system for obesity that goes beyond BMI, incorporating other methods like waist circumference measurement and low-level X-ray body scans to directly measure fat mass.
While there is no fixed obesity threshold, body fat is typically deemed excessive when it exceeds 25% in men and 30–38% in women. Since directly measuring adiposity may be impractical or expensive, alternative health markers such as waist size, waist-to-hip ratio, or waist-to-height ratio are crucial, the researchers explain. However, they indicate that a person with a BMI above 40 likely has high body fat.
The diagnosis of obesity should also consider standard lab tests, medical history, and daily activity information to evaluate how excess body fat could impact an individual’s health, according to study co-author Robert Eckel, an endocrinologist at the University of Colorado Anschutz Medical Campus in Aurora. “These are objective diagnostic criteria that are standardized across global health systems,” he says.
Personalized assessments considering factors like age, gender, and ethnicity are equally important, as certain groups may face health risks at lower BMI thresholds than others, says study co-author Louise Baur, a pediatrician at the University of Sydney, Australia.
Two classifications
Individuals with preclinical obesity have normal working tissues but are at a higher risk of developing health problems compared to those without obesity. They could benefit from counseling and preventive measures like lifestyle changes to lower their risk of developing more severe health issues, the group suggests.
Clinical obesity occurs when excess fat harms organs or significantly hinders daily activities such as walking or dressing. People with clinical obesity may require treatments aimed at improving health and preventing complications.
Rubino emphasizes that this approach is especially crucial given the increasing use of weight-loss drugs, as it helps in accurate diagnosis and effective, cost-efficient treatment.
Addressing stigma
Van Rossum states that this approach, supported by numerous scientific and patient advocacy groups worldwide, reflects mounting evidence of obesity’s health impacts. Another framework published last year also acknowledged that the obesity diagnosis should go beyond BMI to assess its health effects.
Nevertheless, many healthcare providers still view obesity as a matter of willpower rather than a disease fueled by excess fat, regardless of its underlying causes, which may involve hormonal changes and genetic factors, van Rossum notes. In the Netherlands, for instance, a study she co-authored found that most individuals with obesity faced stigma in healthcare settings. This stigma often deters people from seeking care, underscoring the need for improved education and communication on the condition.
While the latest approach aims to provide a more accurate picture of obesity, its impact on the number of diagnoses or the management of the condition in clinics remains uncertain. “We hope that over time, this type of assessment will be integrated into clinical practice guidelines,” Baur says.
This article is reproduced with permission and was first published on January 14, 2025.
