New report proposes redefining obesity by adding body fat and health status to BMI

New guidance from a team of health experts around the world proposes expanding the definition of obesity beyond the popular body mass index (BMI) measure.

The new guidance comes from the Commission on Clinical Obesity, which is led by dozens of medical experts from various medical specialties around the world. The commission recommends the inclusion of body fat measurements and the presence of existing health issues -- and cautions against using BMI alone as an individual measure of health.

The proposal also recommends using the terms "pre-clinical” and “clinical” obesity to offer more nuanced approaches to the evaluation and management of obesity.

Pre-clinical obesity refers to excess fat without organ dysfunction but increased risk of developing clinical obesity and other long-term health problems such as cardiovascular disease, and Type 2 diabetes.

“In other words, their organs are functioning well. They have no metabolic diseases, and they have a fairly good quality of life,” said Dr. Robert Kushner, a commissioner and professor of medicine and medical education at Northwestern University's Feinberg School of Medicine, in an interview with ABC news.

Clinical obesity, by contrast, involves excess fat that directly affects organ function or limits an individual’s ability to conduct daily activities. It can lead to potentially life-threatening complications such as heart attack, kidney failure, and/or stroke.

“The extra body fat is impacting the health or the quality of life of the individual,” said Kushner.

The report further outlines the diagnostic criteria for obesity, combining elevated BMI with at least one abnormal body fat measurement, such as waist circumference, waist-to- hip ratio, waist-to-height ratio, or high direct body fat measurements noted on a scan.

Notably, two or more abnormal body fat measurements could still classify an individual as obese, regardless of BMI.

Obesity is currently defined as a BMI of 30 or above in adults, according to the World Health Organization, affecting 1 in 8 adults. However, using BMI alone to aid in the diagnosis of obesity has its limitations.

“BMI doesn’t take body composition, or how much of body weight is fat or the location of the fat into account," said Dr. Louis Aronne, director of the Comprehensive Weight Control Center at Weill Cornell Medicine, in an email to ABC News. "As a result, someone could be normal weight, but have a high percent of body fat and be at risk of clinical obesity. Additionally, someone could have a high BMI, but have a relatively low body fat percentage."

The commission also stressed that obesity is a chronic disease with major health consequences.

“This is a physical, not a mental or behavioral phenomenon. Obesity as a disease-causing entity either causes or worsens multiple illnesses. Losing weight improves all of them at the same time,” said Aronne.

“By recognizing that some people already have complications of obesity (clinical) and focusing more intensive, expensive treatment on them makes sense as a cost-effective approach. Those who have not reached that point (pre-clinical) can initiate treatment with less intensive, less expensive treatment,” Aronne added.

It is unclear when or if these recommendations will be widely adopted by the medical community.

“We're trying to get this out," said Kushner. "We're putting a stake in the ground to start, getting away from just a blanket diagnosis of obesity for someone who has an elevated BMI. We really need to start identifying individuals who are harmed by their weight.”

ABC News’ Dr. Brent Gawey contributed to this report.

Dr. Jennifer Miao is a board-certified cardiologist and critical care fellow at Yale School of Medicine/YNHH. She is a fellow in the ABC medical news unit.