On Jan. 15, a group of international experts proposed new ways to define and diagnose obesity that place less emphasis on body mass index.
Currently, obesity is defined as a BMI of 30 or higher. However, BMI — a height-to-weight ratio — has long been criticized as an oversimplified and often misleading indicator of health. Under the new recommendations, obesity would be defined by a combination of measures, including waist circumference, evidence of health issues related to excess body fat and BMI.
"We are not throwing out BMI, we are now recommending that individuals have another measurement obtained that more directly gets an estimate of body fat," Robert Kushner, MD, an endocrinologist at Chicago-based Northwestern University and one of the report authors, told NPR News.
The report was authored by 58 experts and published in The Lancet Diabetes & Endocrinology. More than 75 international medical organizations have endorsed the proposal.
The recommendations also put forth two new diagnosis categories: clinical obesity and pre-obesity. The first describes people with evidence of health conditions caused by excess weight, such as heart disease. The latter refers to people at risk of developing a health condition due to their level of body fat.
"What's new is that we try to define obesity by excess body fat, which is what obesity actually is," Dr. Kushner said.
The proposal suggests confirming excess body fat by measuring waist circumference, waist-to-hip ratio or waist-to-height ratio. DEXA scans, which offer a direct measurement of body fat from a screening, are another option, though can be costly and are less accessible than other methods.
"About 40% of the adult population in America has obesity, when it's defined solely by BMI," Dr. Kushner told NPR. "But do all these millions of Americans have a disease? And do they need treatment?"
The guidelines could shift healthcare professionals' perception of who would actually benefit from treatment for obesity, and affect the use of GLP-1 treatments like Wegovy and Zepbound.
A spokesperson for AHIP, a group representing health insurers, told AP News that "it's too early at this point to gauge how plans will incorporate these criteria into coverage or other policies."
While the recommendations aim to add clarity and improve diagnostic accuracy, experts acknowledge they will likely be difficult to implement widely in practice since they carry significant costs.