New definition of obesity challenges current use of BMI

Obesity should be assessed in ways beyond the standard measure of body mass index (BMI), according to a new definition of the condition published by an international commission.

The report, published Tuesday in the journal The Lancet Diabetes & Endocrinology, advocates focusing on the person’s body fat percentage and medical complications, not just their weight.

If the guidelines are widely adopted, they could change doctors’ perceptions of who needs treatment for obesity. They could also impact the use of prescription obesity medications such as Wegovy and Zepbound. The new definition of obesity was supported by 76 organizations around the world.

The commission proposed that BMI not continue to be used as a means of defining obesity, but instead be used as a screening tool to determine who should be tested for excess body fat.

The commission said people who have a BMI over 25 and excess fat but are otherwise healthy should be left alone. You should be monitored and instructed not to gain more weight and possibly lose some.

Her condition would be called preclinical obesity.

Other people with any of the 18 obesity-related diseases – including 13 in children and adolescents – need medical treatment to improve their health and prevent serious organ damage. Conditions include shortness of breath, heart failure, hip or knee pain, metabolic disorders and poorly functioning organs.

Her condition would be called clinical obesity.

The group said people with a BMI of 40 or more have clinical obesity based on their BMI alone – there is no need to determine their body fat.

The commission said it did not know the prevalence of the two types of obesity.

The easiest way for doctors to determine whether someone has excess body fat is to wrap a tape measure around a person’s waist, the group said. If a woman’s waist is more than 87 cm, she most likely has too much fat. For a man, the waist size would be at least 40 inches.

Other tools for healthcare professionals include waist-to-hip ratio, waist-to-height ratio, or DEXA scans, a type of X-ray.

The commission’s 58 experts worked on the report for years and met regularly online. Instead of viewing obesity as a disease, they wanted to look at it differently, said commission chairman Dr. Francesco Rubino, a bariatric surgeon at King’s College London. (Dr. Rubino advises manufacturers of anti-obesity drugs and medical devices.)

The Commission’s approach is consistent with that of the American Heart Association, which supported the report.

“We struggled with the inaccurate methods of defining poor weight,” said Dr. Mariell Jessup, chief scientific and medical director of the association. “How do you define an ideal weight and how do you define an illness weight?”

“We have often been asked: Do you think obesity is a chronic disease? “We felt uncomfortable saying ‘yes’ or ‘no,'” she said. “We think it’s more nuanced.”

Rebecca Puhl, associate director of the University of Connecticut’s Rudd Center for Food Policy and Health, said she viewed the commission’s approach as “an attempt to reduce some misconceptions about obesity that could potentially reduce stigma.”

“Obesity continues to be viewed as a character flaw rather than a complex health issue,” she said.

However, it may be difficult for the new definitions to be widely used.

For years, experts have complained about BMI being used to define overweight and obesity.

The index is easy to measure – all that is needed is a person’s height and weight. It soon became the standard for defining whether people are underweight, overweight or obese.

And BMI is considered a major risk factor for diabetes, heart disease, cancer and other diseases, Dr. David M. Nathan, professor of medicine at Harvard and founder of the Diabetes Center at Massachusetts General Hospital.

He added that a large waist is also a risk factor. But unlike BMI, waist measurements are often carried out incorrectly in the medical field.

It was unrealistic, said Dr. Nathan, “to say that the whole world is going to change like that.”

Equally unrealistic, he continued, is that obesity should not be treated until complications arise. “They think you wouldn’t treat high blood pressure until the person has a stroke,” Dr. Nathan.

Although not everyone who is obese develops a serious health problem, “the number who do not develop weight-related complications is fairly small,” Dr. Nathan added.

Use of the new standard could also impact the new anti-obesity drugs and others that come to market. They are so expensive that some health systems that originally covered them for people with obesity (defined by their BMI) decided they could no longer afford it.

But Dr. David Cummings, a commission member and obesity expert at the University of Washington, suggested limiting it to patients diagnosed with clinical obesity.

The needs of this group are “more compelling,” he said.