Lancet Commission Redefines Clinical Obesity, Moving Beyond BMI
“The Commission reinforces that obesity is a disease and not due to lack of motivation, willpower, discipline, or laziness,” Robert F. Kushner said.
In January 2025, The Lancet Diabetes & Endocrinology published its Commission on the definition of clinical obesity as well as diagnostic criteria. With the new definitions, the Commission has identified preclinical obesity as a risk factor and clinical obesity as a stand-alone illness, according to the authors.
With the new definitions, the Commission has identified preclinical obesity as a risk factor and clinical obesity as a stand-alone illness, according to the authors. | Image Credit: New Africa | stock.adobe.com
“The rationale for these changes was to target monitoring and treatment approaches according to risk status, identify individuals who are experiencing harm to their health at an early stage (before they develop further complications or comorbidities), and allocate resources to those in more immediate [need] of treatment,” Robert F. Kushner, MD, professor in the departments of medicine and medical education at Northwestern University Feinberg School of Medicine, said.
OBESITY, BMI, AND THE CURRENT DIAGNOSTIC SYSTEM
Obesity is an increasingly common issue for patients, especially in the United States. The US obesity epidemic began to emerge around 1980, with only a small rise of approximately 0.5% between 1971 and 1974 to 1976 and 1980. The prevalence rose from 15% in 1976 to 1980, then to 23.3% in 1988 to 1994, and to 30.9% in 1999 to 2000.2
Body mass index (BMI) is currently the standard for classifying obesity and is commonly used as a risk factor for the development of various health issues. BMI is used to estimate the percent of body fat, but this method of measuring obesity has been criticized. In a review about BMI published in Nutrition Today, the author states, “It is time to move beyond the BMI as a surrogate for determining body fat mass...A better means than the BMI for estimating percent of body fat and its relationship to mortality and various morbidities clearly would be desirable.”3
BMI has limitations, the author stated, and the terminology used is prejudicial. The current system is misleading in regard to body fat mass on mortality rates, especially because numerous factors can affect the determination of BMI data. Lifestyle issues, gender, ethnicities, genetic factors, and accumulation of fat with aging can also affect morbidity and mortality rates.3
“The Commission reinforces that obesity is a disease and not due to lack of motivation, willpower, discipline, or laziness. It is a biologically based medical condition and should be treated as such,” Kushner said.
Overweight and obesity can have many risk factors. Although lack of physical activity and unhealthy eating are risk factors, quality of sleep, high amounts of stress, medication, health conditions, genetics, and someone’s environment can also be risk factors.4 Obesity is a chronic health condition, and it is becoming recognized as such.
THE COMMISSION’S NEW DEFINITIONS
The Commission aimed to identify a consensus of classification and definition of obesity—moving away from a single parameter such as BMI.
“Two new terms were presented. Clinical obesity requires confirmation of an obesity status plus signs or symptoms or limitations of daily activities that suggest that excess body fat is causing harm to the body,” Kushner said. “In contrast, preclinical obesity requires confirmation of an obesity status without any signs or symptoms or limitations of daily activities.”
The Commission identified 18 criteria of diagnostics for adults as well as 13 for children and adolescents, which can include breathlessness; chronic, severe knee or hip pain; recurrent or chronic urinary incontinence; or a cluster of elevated blood glucose and blood fats. Kushner stated that the Commission is moving beyond BMI to define and diagnose obesity due to its limitations. Further, BMI can also be used for misdiagnosis, which can include patients who either have high or low muscle mass, according to Kushner.
“Using a pragmatic approach, the Commission recommended that 1 of 3 additional measurements should be performed in addition to BMI to confirm the presence of excess body fat: waist circumference, waist-to-height ratio, or waist-to-hip ratio,” Kushner added. “The Commission also recommended that direct measurement of body fat can be performed if available, such as by bioelectric impedance analysis (BMI) or DEXA. Lastly, if the BMI is 40 or greater, no additional measurements are necessary based on the high probability that the individual has excess body fat.”
As part of the Commission’s editorial, the authors stated that the implementation of the new framework could be more accessible and effective for the management of obesity. For patients who have preclinical obesity, risk mitigation is a key priority.1
“Adopting a new and more precise approach to obesity identification and shifting societal perceptions will take time and effort, but at the heart of these proposals is the aim to improve the lives of people living with obesity,” the authors stated.1
THE PHARMACIST’S ROLE
There has been a rise in prescribing and public interest of glucagon-like peptide (GLP-1) 1 medications, with semaglutide (Wegovy) and tirzepatide (Zepbound) being indicated for weight loss. Semaglutide and tirzepatide have been in shortage since 2022, with tirzepatide being considered resolved in October 2024 and semaglutide being considered resolved in February 2025.5,6
For the Commission framework, Kushner said that the recommendations will not change FDA indications for prescribing obesity medication, but pharmacists should still be aware of the updated ideology around obesity as a disease.
“Excess body fat (obesity) can directly lead to multiple signs and symptoms, or limitations of daily activities. By asking patients ‘how do you think your excess body weight is affecting your health?’ the pharmacist can assess the effectiveness of treatment by noting the improvement or resolution of the patient’s concerns,” Kushner said. “Further commentary and research will likely expand the signs and symptoms used to define clinical obesity. It is important for pharmacists to consider these concepts when conducting future investigations and when counseling patients.”
Kushner stated that, at the current time, there is no known prevalence of clinical obesity or preclinical obesity with the new definition. Further, he added that it is unknown if pharmacological treatment based on BMI alone or based on this new criteria will change the outcome, so there will need to be assessments with the new definition target available resources.
“The Commission reinforces that obesity is a disease and not due to lack of motivation, willpower, discipline, or laziness. It is a biologically based medical condition and should be treated as such,” Kushner said.
