BMI is wrong way to measure obesity, researchers say — here’s what they recommend instead

A group of 58 researchers is calling for a new, better way to measure obesity.

The global team’s recommendations were published in The Lancet Diabetes & Endocrinology on Jan. 14.

Body mass index (BMI) has been the international standard for measuring obesity since the 1980s, according to many sources, though some experts have questioned its validity. 

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A person’s BMI is calculated by dividing his or her weight by the square of his or her height in feet.

"Obesity is a complex problem and has different significance at the individual level," the report's lead author Francesco Rubino, chair of bariatric and metabolic surgery at King’s College London, United Kingdom, told Fox News Digital.

Obesity is a "spectrum," he said, rather than a "single, distinct clinical entity."

Rubino went on, "It is impossible to say if obesity is a disease or not, as disease status cannot coincide with body size or mere excess body fat." 

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The Commission on Clinical Obesity has proposed a "reframing" of obesity that distinguishes between people who have a disease here and now, and those who may have a risk for future disease, Rubino said.

Instead of relying solely on BMI, the researchers recommend also measuring adiposity, which is the amount of excess body fat.

Adiposity can be determined by measuring a person’s waist circumference or taking body scans to measure fat mass, according to the researchers.

The group of experts recommends using two levels of obesity: preclinical and clinical.

With preclinical obesity, the person has excess body fat that has not affected the function of their tissues and organs.

The person may have, however, an increased risk of developing clinical obesity, type 2 diabetes, heart disease and some types of cancer, the researchers noted. 

Clinical obesity is defined 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."

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With clinical obesity, the person may experience "severe end-organ damage, causing life-altering and potentially life-threatening complications," the researchers wrote.

Potential effects of clinical obesity may include heart attack, stroke and kidney failure. 

"As these categories of obesity are entirely new, we can’t measure their relative prevalence in the population," Rubino noted. "Doctors have not yet had the possibility to make such a diagnosis, because many of the organ dysfunctions that characterize clinical obesity have not been routinely assessed so far." 

The researchers call for future studies into these diagnoses. 

"We recommend that clinicians thoroughly assess people with obesity in the clinic and use other measures of body size — waist circumference or others — to understand if an increased BMI level is due to excess body fat or other reasons, like increased muscle mass," Rubino told Fox News Digital.

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When excess body fat — meaning obesity — is confirmed, clinicians should assess individuals to determine whether obesity may have caused any organ dysfunction, the researcher said.

"People with clinical obesity suffer from a chronic illness and should be treated in the same way as people who suffer from any other chronic disease," Rubino said. 

People with preclinical obesity should undergo "evidence-based health counseling, monitoring of their health status over time, and, when applicable, appropriate intervention to reduce risk of developing clinical obesity," they wrote.

Between August 2021 and August 2023, approximately 40% of U.S. adults had obesity, according to the Centers for Disease Control and Prevention (CDC). Around 9.4% of those adults had severe obesity.

Dr. Brett Osborn, a neurosurgeon, longevity expert and fitness competitor based in Florida, agrees that BMI is an "outdated measure" for diagnosing obesity.

"As medicine evolves, it is clear that obesity should no longer be defined solely by physical appearance or weight — or weight relative to height, as in BMI calculations," the doctor, who was not involved in this new research, told Fox News Digital. 

"Instead, the condition must be understood through the lens of metabolic dysfunction."

Obesity isn’t just a disease of excess weight, Osborn said, but a "systemic metabolic disorder requiring nuanced and individualized care."

The condition is better measured by looking at factors like inflammation, insulin resistance and glucose tolerance, according to the doctor.

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In some cases, using BMI can result in "muscular athletes" being labeled as obese, he noted, and people with "normal" BMI can sometimes have "harmful" levels of visceral (abdominal) fat.

Osborn noted that in his own clinic, he and his team do not use BMI, relying instead on visceral fat scores, skeletal muscle mass and body fat percentage. 

Skeletal muscle mass (the muscles that connect to the bones) is critical to physical strength and metabolic efficiency, Osborn said.

For optimal health, he recommends that males aim for 50% skeletal muscle mass relative to total body weight and females target 45% — although other factors, like age and fitness levels, come into play.

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"Remember, your resilience — your ability to ward off disease — resides in your muscle," Osborn added.

"By integrating body composition metrics, metabolic markers and personalized assessments, we can more accurately diagnose obesity and tailor interventions to each individual."