The Lancet Commission on Obesity: Redefining Endocrinology’s Most Notorious Condition

Obesity is a worldwide epidemic, affecting 1 in 8 people worldwide in 2022. Worldwide adult obesity has more than doubled since 1990, with 2.5 billion adults overweight and 890 of these living with obesity in 2022. Additionally, 43% of adults ≥18 years were overweight in 2022, and 16% were living with obesity. In 2024, 35 million children <5 years were overweight.1

Obesity is also associated with a wide variety of comorbidities, impacting almost every aspect of health. From diabetes and cardiovascular diseases to macular degeneration and chronic kidney disease, very few major organs or systems are untouched by increased adiposity.

For decades, the world has lacked a consensus on the classification and definition of obesity. In many cases, it has been labeled a risk factor or a symptom of other diseases. Other studies, however, have indicated it as an indicator of more severe conditions down the line. Patients with obesity are often discussed as a single clinical entity, despite the broad range of health profiles and needs represented among this group. Additionally, obesity has long been described using only body mass index (BMI), which, in recent years, has proven unreliable at best.2

Given this confusion, on January 14, 2025, The Lancet Diabetes & Endocrinology published a Commission detailing the definition and diagnostic criteria of clinical obesity. Aiming to alter the way in which clinicians approach the disease, the Commission effectively distinguished between preclinical obesity – wherein the condition is a risk factor for other diseases – and clinical obesity – when obesity itself represents a standalone illness.2

In this installment of our This Year in Medicine feature series, 3 expert endocrinologists and contributors to the Commission itself were interviewed about their views on this definitive definition of obesity and its implications for the medical world at large. The HCPLive editorial team spoke with W Timothy Garvey, MD, a professor of medicine at the University of Alabama at Birmingham, David Cummings, MD, a professor of medicine at the University of Washington, and Ricardo V Cohen, MD, PhD, the president of the International Federation for the Surgery of Obesity and Metabolic Disorders (IFSO) and director of the obesity and diabetes center at the Hospital Alemão Oswaldo Cruz in Brazil.

This feature explores the controversial decision to separate obesity into the 2 components of preclinical and clinical and the implications of this decision for endocrinology.

The Commission’s Decision

During the interview, Garvey consolidated the Commission’s full 40-page length into a few sentences. “They aimed to recognize that there are patients that have excess adiposity who do not have any complications or related diseases,” Garvey told HCPLive. “They’re healthy, they’re getting around, they’re exercising, they’re happy. And the debate was whether to say they have a disease or not.”

The crux of the Commission’s decision, therefore, was the division obesity into 2 major categories: preclinical and clinical obesity. They argue for a differentiation based on the presence or absence of objective clinical manifestations, specifically altered organ function or the impairment of a patient’s capacity to conduct daily activities. This accounts for the plethora of patients who are clinically obese but display no comorbidities and are in objectively good health.3

Another major decision from the Commission was the differentiation between preclinical and clinical obesity versus metabolically healthy or unhealthy obesity. Typically, unhealthy obesity is defined as a condition posing significant cardiometabolic risk to patients; clinical obesity, however, defines an ongoing illness rather than a method of predicting risk.

Given this, the Commission subsequently moved to provide practical recommendations for management strategies, aiming primarily for risk reduction in preclinical obesity and corrective interventions for clinical obesity. Most prominent among these recommendations is for a new method of confirming excess adiposity.3

To avoid over- and underdiagnosis of obesity, the commissioners encourage clinicians to confirm excess adiposity via 2 individual anthropometric criteria, such as waist circumference, or by direct fat measurement when possible. This circumvents the unreliability of BMI measurements, given their famous inability to account for lean mass.3

Of course, this new diagnosis method is limited in light of the new dichotomous definition of obesity. To accommodate this, the Commission also suggests an examination of medical history, a physical examination, and standard laboratory tests to finalize disease diagnosis.3

However, despite all of these advancements, the Commission stopped short of outright declaring obesity a disease in its entirety. They posited that a blanket definition would cause extreme overdiagnosis, thereby spreading resources and medications thin and incurring enormous costs for healthcare providers and patients alike. This issue has been broached in the past, with a 2021 report from the Association for the Study of Obesity acknowledging the potential financial impacts of such a classification.4

The practical definition for clinical obesity, therefore, is a systemic, chronic illness caused by excess adiposity. It matches the widely accepted criteria of a disease state in certain circumstances, but not in others. This definition also accommodates the famous “obesity paradox,” or the phenomenon in which excess adiposity can coexist with preserved health.3

The Commission’s Implications

After the Commission was released in January, a slew of medical organizations followed suit over the course of the year. For example, the US Center for Disease Control (CDC) issued a statement on August 28, 2025, aiming to solve the persisting challenge of generating specific treatment recommendations for clinical obesity.5

In the document, the CDC suggests incorporating a staging system for the disease, such as the Edmonton Obesity Staging System (EOSS). This program breaks obesity down into 5 stages based on severity, including mental health, clinical status, and physical limitation. EOSS stage 0 includes no obesity-related health issues. Stage 1 includes risk factors, stage 2 accommodates established comorbidities, stage 3 includes chronic diseases, and stage 4 includes end-stage diseases.5

The EOSS has proven a strong predictor of mortality, cardiovascular events, and health care use, but its efficacy has been challenged by other organizations, which suggest other systems such as the cardiovascular-kidney-metabolic syndrome and systemic metabolic disorder schemas. This system prioritizes assessment of organ systems affected by obesity, while the Commission and EOSS recommend a holistic assessment of obesity.5

Additionally, in September 2025, the American Journal of Preventive Cardiology published an article in support of the Lancet Commission’s decision, emphasizing the importance of monitoring body fat to determine the presence of preclinical or clinical obesity. This article proposed an adaptation of the existing ABC model established by the Johns Hopkins Ciccarone Center for the Prevention of Cardiovascular Disease, amending “B is for body weight” to “B is for body fat” – this is in line with the Commission’s focus on excess adiposity.6

Some of the Commission’s impacts have been less direct. For instance, assessing obesity as a disease has allowed for a substantial reduction in the associated stigma. For decades, obesity has been viewed as a condition brought on by poor lifestyle choices or laziness; recontextualizing it as a disease alleviates some of that burden by allowing patients to shed the guilt associated with overweight and obesity.

“Measuring BMI is stigmatizing, it leads to prejudice towards the disease, and leads to the individual feeling guilt,” Cohen told HCPLive. “So, as we shift away from BMI, we shift from guilt to biology. To the person with obesity, this is a huge change, because he or she is sure that he or she has a disease. Diseases may be put into remission.”

Cummings also addressed how the Commission’s decision could potentially impact medication access, as many drugs for obesity are still expensive and relatively difficult to access. With a more efficient and direct method of determining which patients with obesity warrant immediate treatment versus lifestyle interventions, Cummings believes the entire patient population will benefit from easier access to medication.

“I hope this will have an impact in helping payers decide who should get expensive, limited resources to treat obesity,” Cummings said. “I’m speaking of incretin-based medicines here, because those are the expensive ones. They’re life sentences, and the cost of taking them in this country at present is between $950 and $1350 a month.”

Despite these advancements, the Commission is far from a solution to the growing obesity crisis. Without a universal method of diagnosis, or an accessible and affordable means of treatment, high adiposity will continue to dominate as a leading cause of many diseases. However, the Commission does mark a significant step forward in the management of this condition.

References:

1. World Health Organization. Obesity and Overweight. WHO. December 8, 2025. Accessed December 11, 2025. https://www.who.int/news-room/fact-sheets/detail/obesity-and-overweight

2. The Lancet Diabetes & Endocrinology. Redefining obesity: Advancing care for better lives. The Lancet Diabetes & Endocrinology. 2025;13(2):75. doi:10.1016/s2213-8587(25)00004-x

3. Rubino F, Cummings DE, Eckel RH, et al. Definition and diagnostic criteria of clinical obesity. The Lancet Diabetes & Endocrinology. 2025;13(3):221-262. doi:10.1016/s2213-8587(24)00316-4

4. Luli M, Yeo G, Farrell E, et al. The implications of defining obesity as a disease: A report from the Association for the Study of obesity 2021 annual conference. eClinicalMedicine. 2023;58:101962. doi:10.1016/j.eclinm.2023.101962

5. Zahid S, Peng AW, Razavi AC, Yao Z, Blumenthal RS, Blaha MJ. Center stage: Putting Obesity Staging Systems into the spotlight. Preventing Chronic Disease. 2025;22. doi:10.5888/pcd22.250222

6. Zahid S, Peng AW, Razavi AC, Yao Z, Blumenthal RS, Blaha MJ. B is for body fat: a practical implementation of the new clinical obesity definition into preventive cardiology clinic. Am J Prev Cardiol. 2025;23:101281. Published 2025 Sep 1. doi:10.1016/j.ajpc.2025.101281