Obesity Won’t Be Solely Defined by BMI under New Plan for Diagnosis by Global Experts

A man uses measuring tape on his waist in California on Jan. 9, 2025. (AP)
A man uses measuring tape on his waist in California on Jan. 9, 2025. (AP)
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Obesity Won’t Be Solely Defined by BMI under New Plan for Diagnosis by Global Experts

A man uses measuring tape on his waist in California on Jan. 9, 2025. (AP)
A man uses measuring tape on his waist in California on Jan. 9, 2025. (AP)

A group of global experts is proposing a new way to define and diagnose obesity, reducing the emphasis on the controversial body mass index and hoping to better identify people who need treatment for the disease caused by excess body fat.

Under recommendations released Tuesday night, obesity would no longer be defined solely by BMI, a calculation of height and weight, but combined with other measurements, such as waist circumference, plus evidence of health problems tied to extra pounds.

Obesity is estimated to affect more than 1 billion people worldwide. In the US, about 40% of adults have obesity, according to the US Centers for Disease Control and Prevention.

"The whole goal of this is to get a more precise definition so that we are targeting the people who actually need the help most," said Dr. David Cummings, an obesity expert at the University of Washington and one of the 58 authors of the report published in The Lancet Diabetes & Endocrinology journal.

The report introduces two new diagnostic categories: clinical obesity and pre-clinical obesity.

People with clinical obesity meet BMI and other markers of obesity and have evidence of organ, tissue or other problems caused by excess weight. That could include heart disease, high blood pressure, liver or kidney disease or chronic severe knee or hip pain. These people would be eligible for treatments, including diet and exercise interventions and obesity medications.

People with pre-clinical obesity are at risk for those conditions, but have no ongoing illness, the report says.

BMI has long been considered a flawed measure that can over-diagnose or underdiagnose obesity, which is currently defined as a BMI of 30 or more. But people with excess body fat do not always have a BMI above 30, the report notes. And people with high muscle mass — football players or other athletes — may have a high BMI despite normal fat mass.

Under the new criteria, about 20% of people who used to be classified as obese would no longer meet the definition, preliminary analysis suggests. And about 20% of people with serious health effects but lower BMI would now be considered clinically obese, experts said.

"It wouldn't dramatically change the percentage of people being defined as having obesity, but it would better diagnose the people who really have clinically significant excess fat," Cummings said.

The new definitions have been endorsed by more than 75 medical organizations around the world, but it's not clear how widely or quickly they could be adopted in practice. The report acknowledges that implementation of the recommendations "will carry significant costs and workforce implications."

A spokesman for the health insurance trade group AHIP, formerly known as America's Health Insurance Plans, said "it's too early at this point to gauge how plans will incorporate these criteria into coverage or other policies."

There are practical issues to consider, said Dr. Katherine Saunders, an obesity expert at Weill Cornell Medicine and co-founder of the obesity treatment company FlyteHealth. Measuring waist circumference sounds simple, but protocols differ, many doctors aren't trained accurately and standard medical tape measures aren't big enough for many people with obesity.

In addition, determining the difference between clinical and pre-clinical obesity would require a comprehensive health assessment and lab tests, she noted.

"For a new classification system to be widely adopted, it would also need to be extremely quick, inexpensive, and reliable," she said.

The new definitions are likely to be confusing, said Kate Bauer, a nutrition expert at the University of Michigan School of Public Health.

"The public likes and needs simple messages. I don't think this differentiation is going to change anything," she said.

Overhauling the definition of obesity will take time, acknowledged Dr. Robert Kushner, an obesity expert at the Northwestern Feinberg School of Medicine and a co-author of the report.

"This is the first step in the process," he said. "I think it's going to begin the conversation."



How Did a Jet Flip Upside Down on a Toronto Runway and Everyone Survive?

A Delta Air Lines plane that crashed at Toronto Pearson International Airport is seen on February 18, 2025 in Toronto, Canada. (Getty Images/AFP)
A Delta Air Lines plane that crashed at Toronto Pearson International Airport is seen on February 18, 2025 in Toronto, Canada. (Getty Images/AFP)
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How Did a Jet Flip Upside Down on a Toronto Runway and Everyone Survive?

A Delta Air Lines plane that crashed at Toronto Pearson International Airport is seen on February 18, 2025 in Toronto, Canada. (Getty Images/AFP)
A Delta Air Lines plane that crashed at Toronto Pearson International Airport is seen on February 18, 2025 in Toronto, Canada. (Getty Images/AFP)

Investigators are probing the causes of an unusual plane crash at Canada's largest airport on Monday, when a regional jet flipped upside down upon landing during windy weather, sending 21 of the 80 people on board to hospital.

Video shows the Delta Air Lines plane belly up and missing its right wing at Toronto's Pearson Airport, and of the crash that involved no fatalities, circulated widely on social media. The Transportation Safety Board of Canada said on Tuesday that parts of the plane -- a Bombardier-made CRJ900 -- separated after impact and the fuselage came to rest slightly off the right side of the runway, upside down, facing the other direction.

The TSB said it is too early to know what happened and why. Here is what we know about this accident and similar crashes.

HOW DOES A PLANE LAND UPSIDE DOWN?

US aviation safety expert Anthony Brickhouse said aircraft are normally designed to land first on the two main landing gear, and then the nose gear. While the cause of the accident is unclear, the type of impact on the runway likely damaged the landing gear, leaving the plane imbalanced.

Brickhouse said that the plane ending up pointing in the opposite direction speaks to the amount of force and speed that led it to change direction.

"With all the forces and everything going on, if that wing is not there to support the aircraft it's going to go over," Brickhouse said. "It's not something that we see regularly, but when structures start failing, they can't do their job and the aircraft is going to react to the different forces on it."

HOW DID EVERYONE SURVIVE?

Passengers say they were hanging upside down in their seats after the crash.

"All of the passengers were wearing the safety belts. This prevented more serious injuries from occurring," said Mitchell Fox, director of the Asia Pacific Center for Aviation Safety.

Airplane seats are designed to withstand the force of 16 times the normal pull of gravity, or 16Gs, in a crash, whereas wings and fuselage are designed to handle 3-5Gs.

"In an impact-survivable crash, it's more important for the seats to hold up, giving passengers the best chance of survival," said Raj Ladani, a program manager for aerospace engineering at Australia's RMIT University. Good evacuation is key to air accident survivability, as witnessed last year when all 379 people escaped a burning Japan Airlines plane after a runway collision.

"The crew did a remarkable job of evacuating all of the passengers expeditiously," Fox said of the Delta crash.

HAS THIS HAPPENED BEFORE?

While rare, there have been cases of large jets flipping over on landing, including three accidents involving McDonnell Douglas' MD-11 model.

In 2009, a FedEx freighter turned over on landing in windy conditions on the runway at Tokyo's Narita airport, killing both pilots. The left wing was broken and separated from the fuselage attaching point and the airplane caught fire.

In 1999, a China Airlines flight inverted at Hong Kong while landing during a typhoon. The plane touched down hard, flipped over and caught fire, killing three of 315 occupants.

In 1997, another FedEx freighter flipped over at Newark in the United States, with no fatalities.

Brickhouse said it is too early to draw any conclusions from these earlier cases, especially as the MD-11 is a three-engine aircraft and the CRJ900 has two engines mounted toward the back of the aircraft, producing different flight dynamics.

HOW WILL THE INVESTIGATION PROCEED?

Unlike other investigations in which parts of the plane have gone missing, and there are mass fatalities, investigators will be able to interview all 76 passengers and four crew.

Investigators have access to the fuselage and wing, which are on the runway, and the black boxes -- the flight data and cockpit voice recorders -- have been sent for analysis.

"This is going to be a textbook investigation," Brickhouse said. "Some accidents, a lot of the pieces of the puzzle are missing. But right now looking at this accident, all the puzzle pieces are there. It's just you piecing them back together at this point."