Revised obesity definition has implications for clinical management
- 24-10-2025
- Obesity
- Editor's Choice
- News
medwireNews: Changing the definition of obesity to include anthropometric criteria alongside the traditional BMI-based classification increases obesity prevalence by nearly 60%, US study findings indicate.
Writing in JAMA Network Open, Lindsay Fourman and colleagues, from Harvard Medical School in Boston, Massachusetts, say that the “rise was entirely driven by inclusion of individuals with anthropometric-only obesity, defined as having at least 2 elevated anthropometric measures despite a nonelevated BMI.”
The authors explain that a Lancet Commission recently proposed a new definition of obesity that incorporates anthropometric and/or direct measures of body fat that enables better differentiation of excess adipose tissue.
“[T]his guideline has already been endorsed by at least 76 professional organizations, marking a significant shift in how obesity will be conceptualized and classified,” they remark.
The new criteria include three parallel descriptions of obesity:
- Elevated BMI plus at least one elevated anthropometric measure, namely waist circumference, waist-to-hip ratio, or waist-to-height ratio, or BMI greater than 40 kg/m2 regardless of anthropometric measures (designated BMI-plus-anthropometric obesity); or
- At least two elevated anthropometric measures, irrespective of BMI (designated anthropometric-only obesity); or
- Excess body fat as assessed by dual-energy X-ray absorptiometry or similar techniques.
The thresholds for each measurement were sex- and/or race-specific, and these were defined according to the WHO and the Lancet commission.
To determine the clinical implications of the new definition of obesity, Fourman and team analyzed data for 301,026 members of the All of Us cohort (median age 54 years, 61% women), enrolled between 2017 and 2023.
Of these, 42.9% had obesity according to the traditional BMI-based measurement, while 68.6% had obesity according to the new definition, a relative increase of nearly 60%.
Of note, 99.8% of individuals with obesity by the traditional definition also met criteria for BMI-plus-anthropometric obesity. The remaining 0.2% no longer met the criteria as they had a high BMI but no elevated anthropometric measures.
Among the 78,047 individuals with anthropometric-only obesity, 22.3% had a BMI traditionally classified as normal or underweight, while the remainder fell within the overweight category.
The new guideline further divides people with obesity into those with clinical and preclinical obesity based on the presence of organ dysfunction and/or physical limitation.
By this definition, 36.1% of the overall cohort and 52.7% of those with obesity had clinical obesity, with hypertension, physical limitation, and obstructive sleep apnea the most common manifestations. The rates were comparable between men and women, but increased with age, ranging from 8.5% of all 36,396 participants aged 18–29 years to 54.4% of 45,018 individuals aged 70 years and older.
The researchers also looked at the impact of obesity on longitudinal outcomes over a median 4 years of follow-up. They found that, after adjustment for age, sex, and race, individuals with BMI-plus-anthropometric obesity had a significant 3.31-fold higher odds for organ dysfunction, while those with anthropometric-only obesity had a significant 1.76-fold higher odds, relative to people with no obesity.
“These findings support the new definition of obesity by identifying individuals with anthropometric-only obesity as having a heightened risk of adverse health outcomes,” Fourman and co-authors write.
Furthermore, clinical obesity was associated with 6.11-, 5.88-, and 2.71-fold increased risks for incident diabetes, cardiovascular events, and all-cause mortality, respectively, compared with no obesity or organ dysfunction. The risks for incident diabetes and cardiovascular events, but not mortality, were also elevated among people with preclinical obesity, albeit to a lesser degree, at 3.32- and 1.40-fold, respectively.
Finally, the team evaluated the impact of the new guideline, which “recommends pharmacologic therapy for all individuals with clinical obesity and select individuals with preclinical obesity,” on eligibility for obesity pharmacotherapy.
They found that 51.2% of 111,467 participants eligible for obesity pharmacotherapy according to traditional BMI-based indications did not have clinical obesity and may therefore not be eligible for treatment, while 22.2% of 69,894 individuals with clinical obesity by the new definition did not meet current criteria for glucagon-like peptide (GLP)-1 receptor agonist treatment.
“Thus, implementation of the new framework may have significant ramifications for patients, including existing GLP-1 [receptor agonist] users, and creates a compelling need to evaluate use of antiobesity medications within this redefined target population,” Fourman et al remark.
The authors conclude: “Our findings support inclusion of anthropometric-only obesity within the new obesity definition and affirm the value of clinical obesity in identifying individuals at highest risk of adverse health outcomes.”
They add: “At the same time, our results highlight critical gaps in knowledge regarding anthropometric-only obesity, preclinical obesity, and the shifting target population for obesity pharmacotherapy, underscoring the need for further research to inform evidence-based care of these groups.”
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