A new approach to defining obesity could help physicians better determine which patients need more intensive treatment by focusing on the effects of excess adiposity on organs and tissues rather than relying primarily on whether a person meets a set of metabolic risk thresholds.
In a new review published in The Journal of Clinical Endocrinology & Metabolism, researchers from LSU's Pennington Biomedical Research Center examine the concept of "metabolically healthy obesity" and argue that a newer framework distinguishing preclinical obesity from clinical obesity provides a more biologically grounded and clinically actionable approach.
The review, " Does Metabolically Healthy Obesity Really Exist: Going Toward New Definitions ," was authored by Dr. Christian Rodriguez , postdoctoral researcher, and LSU Boyd Professor Dr. Eric Ravussin . The paper examines how the traditional classification of metabolically healthy obesity (MHO) and metabolically unhealthy obesity (MUO) has influenced treatment decisions and why the newer outline developed by the Lancet Diabetes & Endocrinology Commission on the Definition and Diagnosis of Clinical Obesity may offer a better path forward.
The traditional MHO/MUO framework generally classifies people with obesity based on the presence or absence of metabolic abnormalities. Under that approach, individuals with metabolically unhealthy obesity may be candidates for more intensive lifestyle interventions and pharmacotherapy, while those classified as having metabolically healthy obesity may initially receive structured lifestyle support, with more intensive treatment considered if their metabolic health worsens or other risk factors emerge.
The challenge is that the definition of MHO varies considerably across studies and is often not a stable condition. Individuals classified as having MHO may develop metabolic abnormalities over time, complicating treatment plans based on the assumption that their obesity is currently "healthy."
"Metabolically healthy obesity helped researchers recognize that obesity does not affect every person in exactly the same way," Dr. Ravussin said. "But the classification is difficult to use as a foundation for long-term treatment because the definitions vary and metabolic health can change. A person who is considered metabolically healthy today may not be metabolically healthy tomorrow."
The preclinical/clinical obesity framework proposed by the Lancet Commission takes a different approach. Rather than defining obesity primarily by the presence or absence of a specific cluster of metabolic risk factors, it considers whether excess adiposity is causing dysfunction in organs or tissues or limiting a person's ability to perform daily activities.
This means that preclinical obesity describes individuals with confirmed excess adiposity who do not currently have evidence of obesity-related organ or tissue dysfunction. These individuals may benefit from structured lifestyle interventions, regular monitoring of cardiometabolic health and shared decision-making about pharmacotherapy when individual risk is elevated.
On the other hand, clinical obesity is defined by excess adiposity accompanied by obesity-related organ or tissue dysfunction or significant limitations in daily activities. For these individuals, evidence-based pharmacotherapy and, when appropriate, metabolic or bariatric surgery may be considered alongside treatment of the specific health problems associated with obesity.
Importantly, the framework also changes how treatment success may be evaluated. Rather than measuring success solely by the amount of weight lost, the goal is to improve or resolve the organ or tissue dysfunction that defines a person's clinical obesity.
"Moving from the question 'Is this person metabolically healthy or unhealthy?' to 'Is excess adiposity affecting the function of the body?' gives us a more clinically meaningful way to think about obesity," Dr. Rodriguez said. "The framework allows us to identify people who may benefit from prevention and monitoring while also recognizing when obesity has progressed to a disease state requiring more intensive treatment."
The new approach builds on the work of the Lancet Diabetes & Endocrinology Commission on the Definition and Diagnosis of Clinical Obesity. Three Pennington Biomedical researchers – Dr. Ravussin, Dr. Philip Schauer and Dr. John Kirwan – served on the 56-member international Commission that developed the new method for defining and diagnosing obesity.
The authors note that it is still evolving and will require additional research to validate its diagnostic criteria and develop tools for consistent implementation in clinical practice and public health. The review concludes that the concept of metabolically healthy obesity has helped advance understanding of the biological diversity of obesity but is limited by inconsistent definitions, its potentially temporary nature and its focus on a relatively narrow set of metabolic risk factors.
About the Pennington Biomedical Research Center
The Pennington Biomedical Research Center is at the forefront of medical discovery as it relates to understanding the triggers of obesity, diabetes, cardiovascular disease, cancer and dementia. Pennington Biomedical has the vision to lead the world in promoting nutrition and metabolic health and eliminating metabolic disease through scientific discoveries that create solutions from cells to society. The Center conducts basic, clinical and population research, and is a campus in the LSU System.
