BMI is a 53-year-old metric that 58 expert researchers suggest officially needs an update—here's what they say is the more reliable way to determine healthy body weight.
Want To Know If You’re Overweight? Forget BMI—Measure This, Says a Team of Experts
Published on Jan. 17, 2025
According to the National Library of Medicine, body mass index—commonly called “BMI”—was introduced as a system of bodily measurement in 1972. BMI calculates a correlational measurement between height and weight to determine whether an individual is obese or living at a healthy weight. However, in recent years experts have increasingly called out the widely used screening tool, saying BMI serves as a poor proxy for actual health.
A breaking January 2025 report published in the medical community’s highly regarded journal, The Lancet, has re-examined the definition of obesity as a chronic disease. Reported by The Lancet Diabetes and Endocrinology Commission, the report suggests that BMI does not define the condition nor replace clinical judgment in identifying it. In fact, the report suggests that BMI can underestimate or overestimate one’s body fat, convoluting many patients’ healthcare needs. BMI doesn’t take into account factors like muscle mass or visceral fat—both of which are consistently shown to have significant impact on the development of chronic diseases and even longevity.
The commission consisted of a group of 58 experts working in a range of medical specializations and countries, including professionals “with lived experience of obesity” to be inclusive of multiple perspectives. Their aim was to establish unbiased criteria for disease diagnosis, therapeutic interventions, and public health strategies for obese individuals.
As a result, they suggest BMI does a poor job of diagnosing clinical obesity. The team defines clinical obesity as a chronic, systemic illness in which excess body fat causes changes or damage in the tissues, the organs, or the entire body. They note that cases of clinical obesity can result in “severe end-organ damage, causing life-altering and potentially life-threatening complications”—for instance, heart attack, stroke, and kidney failure. (Meanwhile, “preclinical obesity” represents a state of excess body fat with “preserved function of other tissues and organs and a varying, but generally increased, risk of developing clinical obesity and several other non-communicable diseases” like certain cancers, heart disease, type 2 diabetes, and more.)
Rather than relying on BMI to help assess overall health risk, the team suggests a set of other measurements: “Excess adiposity [body fat] should be confirmed by either direct measurement of body fat, where available, or at least one anthropometric criterion (e.g. waist circumference, waist-to-hip ratio, or waist-to-height ratio) in addition to BMI, using validated methods and cutoff points appropriate to age, gender, and ethnicity.” (NPR adds that a DEXA scan was also listed among the methods the researches suggest can effectively determine obesity, when finances and availability make it possible.)
The research team notes that only in cases of very high BMI can we reasonably assume dangerous levels of excess body fat without additional metrics to confirm. Otherwise, individuals should speak with their doctors about using alternate means of assessment, and to make an individualized plan for care.
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