NEW YORK, NY — A new study suggests that more than 75% of adults in the United States may meet criteria for obesity when using a revised definition that expands beyond traditional body mass index (BMI) measurements, researchers reported Monday. The findings underscore concerns that existing methods may significantly underestimate the true prevalence of obesity and related health risks in the population.
For decades, BMI has been the standard measure for classifying obesity, with a BMI of 30 or higher signaling the condition. Under that system, roughly 40% of U.S. adults meet obesity criteria. However, the new study applied a broader set of measurements including waist circumference and body-fat indicators — measures backed by the Lancet Diabetes & Endocrinology Commission and endorsed by more than 70 health organizations globally and found the rate of obesity jumped to over 75%.
The research team, which included experts from institutions like Beth Israel Deaconess Medical Center, Harvard and Yale, analyzed data from more than 14,000 adults participating in the National Health and Nutrition Examination Survey (NHANES) from 2017–2023. When both traditional BMI and waist-based measurements were used together, a much larger segment of the population was classified as having excess body fat.
One striking finding was that nearly four in 10 adults with a “normal” BMI were identified as having excess body fat when waist measurements were accounted for, indicating that BMI alone may miss people at risk for weight-related health problems such as high blood pressure, diabetes and heart disease.
Researchers caution that while the new criteria may better quantify obesity and health risk, additional research and age-specific standards will be needed before the expanded definition is widely adopted in clinical practice. They noted that nearly all adults aged 50 and older would be classified as having obesity under the new measure, raising questions about how best to tailor risk assessments.
Health experts say these findings highlight the limitations of BMI and support broader use of measures that account for body composition and fat distribution. Tools like waist-to-height ratio and waist circumference may better reflect underlying risks than weight-alone metrics since they help distinguish between fat and muscle and detect abdominal adiposity, a factor linked to heart disease risk.
The study has sparked discussion about how obesity should be defined and diagnosed in clinical settings, with implications for public health policy, medical treatment eligibility, and preventive care strategies. As health providers consider whether and how to incorporate the expanded definition, the research emphasizes that a majority of American adults may have excess body fat that isn’t fully captured by traditional measurements.
