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A major shift in the way obesity is defined could significantly increase the number of people classified as having the condition, according to a new study published in the Annals of Internal Medicine. The research, based on data from the US National Health and Nutrition Survey (NHANES) spanning 1999 to 2018, found that about 1 in 5 individuals previously considered merely overweight by Body Mass Index (BMI) standards would now be classified as having obesity under the European Association for the Study of Obesity’s (EASO) new framework.
Beyond BMI: A More Nuanced Approach
The EASO framework, published in July 2024, defines obesity as either a BMI of 30 or higher, or a BMI of 25 or higher combined with a waist-to-height ratio of at least 0.5, plus the presence of any obesity-related medical, functional, or psychological complications. This approach aims to capture health risks related to central fat distribution and associated complications, rather than relying solely on BMI.
Lead author Dror Dicker, MD, emphasized the significance of these findings: “Even people who are so-called living with overweight can be defined as living with obesity, meaning they have a higher risk for mortality, and by definition, more complications…These patients in the past were transparent,” he told Medscape Medical News.
The study revealed that people reclassified as having obesity under the new criteria do have an increased risk of mortality compared to those with normal weight and no comorbidities. However, their risk is not higher than adults of normal weight who already have other health conditions. This nuance has led some experts to question the clinical and public health relevance of the new definition, suggesting that comorbidities themselves, rather than the new obesity classification, may be the primary drivers of increased risk.
Christina C. Wee, MD, Senior Deputy Editor at Annals of Internal Medicine, noted, “The findings imply that the EASO definition, while potentially useful for identifying morbidity risk and guiding clinical care, does not significantly enhance mortality prediction beyond traditional BMI thresholds”.
A Broader Movement to Redefine Obesity
The EASO framework is part of a broader movement to update obesity definitions globally. Other recent proposals, such as those from the International Atherosclerosis Society and the Lancet Commission, incorporate measures like waist circumference and direct assessments of body fat. These efforts reflect growing recognition that BMI alone may not accurately identify all individuals at risk due to excess body fat, particularly those with higher central adiposity.
Despite these advances, challenges remain in clinical practice. Many primary care providers still rely on BMI and may lack the tools or training to measure waist circumference accurately. Obesity expert Donna H. Ryan, MD, observed, “Most of the effort is to shift to a measure of central fat measurement, but most offices don’t even have a tape measure and if they do, they don’t measure regularly or correctly”.
Disclaimer: This article is based on information from a recent Medscape report and related medical publications. The new obesity definitions and their clinical implications are still under debate within the medical community. Individuals concerned about their health or weight should consult with qualified healthcare professionals for personalized advice and diagnosis.
