From 2022 to 2024, The Lancet Diabetes & Endocrinology Commission on Clinical Obesity, a distinguished panel of the world's leading obesity experts, convened virtually each month to help establish new recommendations for diagnosing obesity.
Recognizing that there was no global consensus on a clinical definition and that body mass index (BMI) alone wasn’t a sufficient measure, the commission published their guidelines in The Lancet Diabetes & Endocrinology in January 2025.
Blandine Laferrère, M.D., Ph.D., an endocrinologist at NewYork-Presbyterian and Columbia and a researcher at the New York Nutrition Obesity Research Center at Columbia, is a member of the commission and has been researching obesity for over 30 years. Below, she explains how the commission came to its recommendations and why having a clinical definition of obesity leads to better patient care.
Why BMI Alone Is Unreliable
Body mass index (BMI) has long been the standard for screening patients for obesity and identifying those in need of weight management interventions, but obesity experts have known for years that it is not a perfect measure.
Calculating BMI only requires knowing a patient’s height and weight, and the current threshold for obesity (a BMI over 30kg/m2) has been based primarily on data from people of European descent. So, on its own, BMI doesn’t account for the different types of body compositions that exist; for example, someone with a high BMI but also high lean muscle mass would be considered as having obesity, but that would be an incorrect diagnosis. There are people with a BMI below 30 who have increased fat in the upper part of their body may be at high risk for obesity and related diseases, and those who are above 30 who are relatively healthy.
We recommend that people with preclinical obesity be encouraged to continue living a healthy lifestyle, but they do not necessarily need to target active weight loss with various interventions.
— Dr. Blandine Laferrère
As a member of The Lancet Diabetes & Endocrinology Commission, we sought to develop better definitions for preclinical and clinical obesity that can help us more accurately determine who is most at risk. One of our guidelines is to look at BMI in conjunction with waist circumference, which is a simple measure of fat distribution and can help determine if a patient has excess adiposity, or body fat. Having excess fat is defined as a waist circumference exceeding 34.6 inches in women and 40 inches in men. This is not a new concept; the finding that people who are apple-shaped have a higher risk of cardiovascular disease than those who are pear-shaped dates back to the 1930s.
The new definitions also take into account the effects of obesity on the body's organs, including the liver, heart, pancreas, kidneys, and respiratory system. This is very important so we can focus the resources we have, which are not unlimited, on the people who need them most.
Preclinical Versus Clinical Obesity
Organ damage is a differentiating factor between preclinical and clinical obesity and helps us understand how to care for people in each group. The Lancet Commission formally defines clinical obesity as a chronic, systemic illness characterized by alterations in the function of tissues, organs, the entire individual, or a combination thereof, due to excess adiposity.
By providing a clinical and more nuanced definition of obesity, we can differentiate it from ‘healthy overweight’ to focus weight-loss interventions on those most at risk and fight some of the stigma surrounding it.
— Dr. Blandine Laferrère
Common forms of organ damage and dysfunction associated with obesity include dyspnea, cardiac failure, fatty liver, liver cirrhosis, metabolic complications like diabetes, sleep apnea, urinary incontinence, and debilitating joint pain. Even the inability to perform activities of daily living, such as dressing oneself or moving around, can be taken into consideration. Just one of these disorders, coupled with adiposity, is sufficient to warrant a diagnosis of clinical obesity. These patients are those most in need of resources, such as intensive lifestyle, weight loss medications or bariatric surgery.
Preclinical obesity, by contrast, is defined as adiposity without organ damage. That could be someone who may have a BMI that falls within the old definition of obesity, but who is relatively fit and participates in physical activity regularly. We recommend that people with preclinical obesity be encouraged to continue living a healthy lifestyle and not continue to gain weight, but they do not necessarily need to target active weight loss with pharmacological interventions.
The Importance of Labeling Obesity as a Disease
Despite its significant impact throughout the body, obesity is still not widely recognized in the medical community as a disease but rather as a risk factor. However, for someone who has hypertension, diabetes, or sleep apnea, obesity is often at the center of it, and therefore it must be considered a disease.
By providing a clinical and more nuanced definition of obesity, we can differentiate it from “healthy overweight” to focus weight-loss interventions on those most at risk and fight some of the stigma surrounding it. Recognizing obesity with a better clinical definition may also influence the way insurance companies reimburse to ultimately provide better access to treatment.
While we’ve seen early support and enthusiasm for the new guidelines, it’s too soon to know if they will be widely accepted. But what we do know is that this is not a disease that can be tackled only by obesity specialists. We also need primary care physicians to be trained in obesity medicine so they can help patients achieve or maintain healthy weight and body fat before it significantly impacts their health. By changing physicians’ perceptions of obesity, we ultimately hope to improve the quality of care for patients.
