A collective of international experts has put forth a new approach to the classification and diagnosis of obesity, seeking to lessen dependence on the often-debated body mass index (BMI) and aiming to more accurately identify individuals requiring treatment for this condition resulting from excess body fat.
On Tuesday evening, a set of recommendations was unveiled that suggests redefining obesity not just by BMI, which measures height against weight, but by integrating additional metrics, including waist circumference along with indicators of health issues linked to excess body weight.
Globally, obesity is estimated to impact over 1 billion individuals. In the United States alone, approximately 40% of adults are categorized as obese, according to the Centers for Disease Control and Prevention.
Dr. David Cummings, an obesity specialist at the University of Washington and one of the authors behind the comprehensive report published in The Lancet Diabetes & Endocrinology journal, stated, “The aim is to establish a more precise definition to ensure we focus support on those who genuinely require it.”
The report proposes two novel diagnostic classifications: clinical obesity and pre-clinical obesity. Individuals characterized with clinical obesity would fulfill the criteria of BMI and present other obesity-related markers alongside physical manifestations of health issues caused by excessive weight. These health problems could encompass conditions such as heart disease, high blood pressure, liver or kidney diseases, or severe chronic joint pain. Such individuals would qualify for various treatments, including dietary changes, exercise programs, and obesity medications.
Conversely, pre-clinical obesity is defined as a risk status where individuals may be prone to these health complications but currently do not exhibit any ongoing medical conditions associated with obesity.
Traditionally, BMI has been criticized for its limitations, leading to both over-identification and under-identification of obesity cases. Currently, obesity is recognized with a BMI of 30 or greater. However, the report highlights that individuals with excess body fat may not always register a BMI above 30, and individuals with substantial muscle mass, such as athletes, may show inflated BMI values while possessing normal fat levels.
Preliminary analysis indicates that under the new guidelines, around 20% of individuals previously categorized as obese might no longer fit this definition while approximately 20% of individuals with significant health risks at lower BMI levels would now be regarded as clinically obese.
According to Cummings, “The overall percentage of the population defined as obese may not change dramatically, but it will enhance the precision in diagnosing those who genuinely have clinically significant excess fat.”
More than 75 medical organizations internationally have supported the new definitions, though it remains uncertain how quickly or widely these could be implemented in real-world practice. The report highlights that putting these recommendations into action “will incur substantial costs and workforce challenges.”
In response to these developments, a spokesperson for AHIP, the trade group for health insurers, stated, “It is premature to determine how plans might integrate these criteria into their coverage policies or frameworks.”
Practical considerations are also important, as Dr. Katherine Saunders from Weill Cornell Medicine pointed out. While measuring waist circumference seems straightforward, varying protocols exist, many health practitioners lack accurate training, and standard tape measures may not suffice for many individuals with obesity.
Moreover, distinguishing between clinical and pre-clinical obesity would necessitate thorough health evaluations and lab testing, she observed.
“For a new classification system to gain traction, it needs to be incredibly quick, affordable, and dependable,” she stated.
Kate Bauer, a nutrition specialist at the University of Michigan School of Public Health, indicated that these new definitions could lead to confusion among the public. She remarked, “The general populace appreciates and requires clear, straightforward messaging. I doubt this distinction will significantly affect perceptions and understanding of obesity.”
Dr. Robert Kushner, an obesity specialist at Northwestern Feinberg School of Medicine and another co-author of the report, recognized that revising the definition of obesity would be a gradual process. “This is merely the initial step in the journey,” he noted. “I believe it will spark important conversations moving forward.”
