New report redefines obesity beyond BMI
A new report published in The Lancet Diabetes and Endocrinology is set to reshape how obesity is diagnosed, moving beyond the traditional Body Mass Index (BMI) measurement to a more comprehensive definition based on adiposity and its impact on the body.
The 2025 report, authored by a team of over 50 international experts, defines obesity as a condition characterised by excessive body fat that can lead to dysfunction in tissues, organs, or the body as a whole. This new approach aims to distinguish between individuals with preclinical obesity, those with excess adiposity but no immediate health complications, and those with clinical obesity, where fat accumulation is already affecting vital organs and bodily functions.
For decades, BMI has been the primary tool for assessing obesity, but experts argue it is insufficient in accurately diagnosing the condition. BMI does not differentiate between fat and muscle mass, nor does it account for how body fat is distributed or its impact on overall health.
Professor Francesco Rubino, a bariatric surgeon at King’s College London and one of the study’s lead authors, emphasised that BMI should only be used as a population-level screening tool, rather than a diagnostic measure for individuals. Instead, the new criteria recommend assessing excess adiposity using direct body fat measurements or anthropometric measures such as waist circumference and waist-to-hip ratio.
According to the report, clinical obesity is a chronic and systemic disease that results in impaired function of organs, tissues, or the body as a whole. It is associated with severe health risks, including heart disease, stroke, type 2 diabetes, and kidney failure.
In contrast, preclinical obesity refers to excess adiposity without immediate health complications. However, individuals with preclinical obesity remain at high risk of developing clinical obesity and related conditions in the future.
Despite the fact that an estimated half of the population is living with obesity, only 1 per cent receive appropriate treatment. Experts stress that treating obesity should go beyond weight loss interventions. Dr Carolina Solis-Herrera, Chief of the Division of Endocrinology at the University of Texas, argues that care should be tailored to each individual’s medical needs rather than focusing solely on weight reduction or treating comorbidities.
The report also challenges widespread misconceptions about obesity, including being overweight means carrying excess fat, but it does not automatically indicate a chronic disease. The authors also highlight that it’s not just about exercising more, as while physical activity is beneficial, obesity is a complex public health issue requiring access to medical treatment and policy-driven solutions.
The findings from The Lancet report underscore the need for updated diagnostic tools and improved access to obesity treatment. Researchers hope that shifting the definition of obesity will lead to better healthcare strategies, early interventions, and comprehensive support for individuals at risk.