Expanded Obesity Definition Would Classify Three-Quarters of U.S. Adults as Obese, Study Finds

A new analysis shows that adding body fat distribution and health indicators to traditional BMI measurements dramatically increases the share of American adults who meet obesity criteria.

By yourNEWS Media Newsroom

A newly published study suggests that far more Americans could be classified as obese under an expanded medical definition that moves beyond body mass index alone and incorporates additional measures of body fat and related health risks.

Researchers from Harvard University, Yale New Haven Health, and Beth Israel Deaconess Medical Center reported that approximately 75 percent of U.S. adults would meet the criteria for obesity using the revised approach, compared with about 40 percent when obesity is defined strictly by BMI. The findings were reported by ABC News.

The analysis is based on recommendations from the Lancet Diabetes & Endocrinology Commission, a collaboration between the medical journal and King’s Health Partners Diabetes, Endocrinology and Obesity, which proposed redefining obesity to include waist circumference, waist-to-hip ratio, and waist-to-height ratio in addition to BMI. While more than 70 medical organizations worldwide have endorsed the updated definition, the study’s authors noted that its real-world impact had not previously been evaluated at a national level.

“BMI is the standard measure for determining criteria for obesity. It’s the most widely known metric,” said Dr. Erica Spatz, a cardiologist at Yale School of Medicine and a co-author of the study. She added that BMI alone fails to account for adipose tissue, a type of body fat that insulates organs, stores energy, and produces hormones that regulate appetite.

According to Spatz, adipose tissue is less visible than other fat deposits but “is more associated with high blood pressure, diabetes, and heart disease,” underscoring the limitations of relying solely on BMI.

The research, published in JAMA Network Open, analyzed data from the National Health and Nutrition Examination Survey, a nationwide program run by the Centers for Disease Control and Prevention. The survey tracks health indicators among children and adults across the United States.

The team examined data from more than 14,000 participants representing an estimated 237.7 million U.S. adults between 2017 and 2023. When the expanded criteria were applied, researchers estimated that 75.2 percent of adults met the definition of obesity, compared with 40 percent when BMI alone was used.

Dr. Fatima Cody Stanford, an associate professor of medicine and pediatrics at Massachusetts General Hospital and Harvard Medical School who was not involved in the study, said the findings highlight the scale of the challenge obesity poses to public health.

“We do have a major problem,” Stanford said. “Obesity is by far the most significant chronic disease in human history. We need to be doing a better job of treating it, make sure that we have the clinicians that are trained to identify not only obesity itself, but the over 230 chronic diseases associated with it, and making sure that we have a healthier society.”

The authors of the study emphasized that the revised definition is intended to improve identification of health risks rather than simply expand diagnostic labels, arguing that more precise measurements could lead to earlier intervention and more effective treatment strategies.