In the evolving field of bariatric medicine, we’re witnessing a significant shift in how we define and understand obesity. Recent developments, led by a group of 58 global experts across multiple medical specialties—including individuals with lived experience of obesity—have provided a new and much-needed framework for defining this condition. The implications of this redefinition are far-reaching, with the potential to improve how we diagnose, treat, and perceive obesity in clinical practice and public health.
Beyond BMI: A Holistic Approach to Obesity
For years, Body Mass Index (BMI) has been the go-to metric for defining obesity. However, we’ve long recognized its limitations. BMI is a population-level tool that does not account for individual variations in adiposity, fat distribution, or health outcomes. As a result, it can both underestimate and overestimate the risks associated with obesity. This new definition emphasizes that BMI should only be used as a screening tool or for epidemiological studies—not as a definitive measure of health at the individual level.
Instead, the focus has shifted to defining obesity based on excess adiposity—a term that encompasses both the quantity and distribution of body fat—and its impact on organ and tissue function. This approach provides a more nuanced and accurate understanding of obesity as a complex and multifactorial condition.
Clinical and Preclinical Obesity: A New Framework
The commission introduces two distinct categories: clinical obesity and preclinical obesity:
- Clinical Obesity: Defined as a chronic, systemic illness resulting from excess adiposity that disrupts the function of organs, tissues, or the body as a whole. This can lead to severe complications such as heart attacks, strokes, and kidney failure. Diagnosis requires evidence of reduced organ or tissue function or significant limitations in daily activities due to obesity.
- Preclinical Obesity: A state of excess adiposity without current organ or tissue dysfunction but with an elevated risk of developing clinical obesity and related diseases such as type 2 diabetes, cardiovascular disease, and certain cancers. Preclinical obesity provides a crucial window for early intervention to prevent progression to more severe stages.
Implications for Diagnosis and Treatment
This redefinition prioritizes individualized care and evidence-based interventions. For people with confirmed obesity status, it is recommended to:
- Confirm Excess Adiposity: Using direct measures of body fat or validated anthropometric criteria such as waist circumference, waist-to-hip ratio, or waist-to-height ratio, in addition to BMI.
- Assess Organ and Tissue Function: To determine whether obesity has progressed to the clinical stage.
- Tailor Treatment Plans: For individuals with clinical obesity, timely interventions aim to improve or, where possible, reverse obesity-related health issues and prevent end-organ damage. For those with preclinical obesity, health counseling, monitoring, and preventive measures can mitigate risks and promote long-term well-being.
Addressing Stigma and Bias
Perhaps one of the most profound aspects of this new framework is its emphasis on addressing weight-based stigma and bias. Obesity has often been misconstrued as a failure of individual responsibility, overshadowing its complex biological, environmental, and societal causes. The commission highlights the importance of training healthcare professionals and policymakers to combat stigma and ensure equitable access to evidence-based treatments.
What This Means for Patients
As a bariatric surgeon, I’m encouraged by this more comprehensive and compassionate approach to obesity. For patients, this new definition means:
- More accurate and personalized diagnoses.
- Timely interventions to prevent disease progression.
- A focus on health outcomes rather than arbitrary weight targets.
- Reduced stigma and greater understanding of the challenges they face.
Moving Forward
This new definition represents a paradigm shift in our understanding of obesity. It acknowledges the complexity of the condition, prioritizes early intervention, and underscores the importance of treating obesity as a chronic illness. Most importantly, it brings us one step closer to providing the compassionate and effective care that every patient deserves.
If you are concerned about your weight or considering bariatric surgery, I encourage you to consult with a qualified specialist to explore your options. Together, we can develop a plan tailored to your unique needs and health goals.
References
- Rubino, F., Cummings, D. E., Eckel, R. H., Cohen, R. V., Wilding, J. P., Brown, W. A., … & Mingrone, G. (2025). Definition and diagnostic criteria of clinical obesity. The Lancet Diabetes & Endocrinology.
