Redefining Obesity in Veterinary Medicine: Making the Case for “Clinical Obesity”
Aligned with the Lancet Commission on Clinical Obesity
The words we use in veterinary medicine matter, particularly regarding obesity.
What healthcare professionals say, and how they say it, influences the acceptance of preventive measures, diagnoses, therapeutic plans, and treatment adherence. Choose the right words and express them effectively, and patients benefit. Select the wrong words, and we may risk patient outcomes and jeopardize client relationships.
The terms used to describe obesity in animals have the power to inspire change and promote health, or to fuel bias and stigma that cause patients to suffer. Offensive words such as “fat” and “obese” can serve to judge and blame, while substitutions such as “chonky” and “fluffy” diminish the severity of the health impacts caused by excess adiposity. The veterinary profession needs a better, scientifically valid vocabulary for more precise, empathetic, and effective communication about pet obesity.
Obesity, Blame, and Shame
“Obesity” is unique in that it carries emotional and societal connotations absent in most medical conditions. Many mistakenly believe that obesity results solely from a lack of willpower, intentional overeating, or under-exercising, and that it can be “cured” through self-discipline alone.
Weight gain is often unfairly viewed as a personal choice, with those affected seen as entirely to blame. In veterinary medicine, pet owners are frequently held solely accountable for their pet’s body condition, and obesity is often framed as a failure to be a “good pet parent.”
While these sentiments contain some truth, they fall far short of the full picture. The causes of obesity in both humans and animals are multifactorial, including genetics, hormonal imbalances, environmental endocrine disruptors, alterations in the microbiome, lifestyle choices, and more.
Like many other chronic diseases, obesity typically results from a combination of factors. Yet we rarely blame a patient for developing cancer, kidney disease, or even arthritis. In fact, we often console those affected by these conditions with phrases like “It’s not your fault.” So why don’t we approach obesity with the same compassion and understanding?
Obesity is an active disease state that negatively affects quality of life, reduces life expectancy, and causes or complicates nearly every other medical condition. It is also an emotionally charged issue, burdened by a significant stigma that often acts as a barrier to care.
Few diseases so urgently demand our most compassionate and empathetic language.
Defining Obesity in Evidence-Based Terms
For the past several years, I have been advocating for a revision in how we define obesity in animals. The term “obesity” has become polarizing, with its definition varying widely among veterinary professionals. Relying solely on body condition graphics and images to “diagnose” a disease is scientifically problematic.
Further complicating the issue is how the general public and media perceive obesity as an undesirable aesthetic or lifestyle choice rather than a serious disease, particularly in companion animals. Terms like “chonky cats” and “greedy dogs” are often used to defuse emotional triggers and reduce blame. However, these expressions also trivialize the life-threatening complications of obesity.
Words matter, and that is where the term “clinical obesity” comes in.
A Global Shift to “Clinical Obesity”
The Lancet Diabetes and Endocrinology Commission on Clinical Obesity hosted a global online event on January 16, 2025, to discuss shifting the conversation toward “clinical obesity.” More than a year earlier, the commission had announced that new terminology was necessary, especially in response to the global surge in the use of GLP-1 medications. The commission’s peer-reviewed findings were published in the journal a few days before the event.
The authors aimed to provide a medically coherent framework for disease diagnosis and to settle the ongoing dispute over obesity as a disease. We are working to do the same for veterinary medicine.
It’s Time for “Clinical Obesity” in Veterinary Medicine
The Association for Pet Obesity Prevention (APOP) and the World Pet Obesity Association (WPOA) have been advocating for the use of the term “clinical obesity” in veterinary medicine for the past two years. Unfortunately, many in organized veterinary medicine continue to reject the idea that pet obesity is a distinct disease, or that our current language has fallen short. Some of our leaders cling to the notion that we can “shame and blame” our way out of this crisis, despite decades of evidence in human and pediatric medicine that prove otherwise. Change is hard.
The goal of defining “clinical obesity” is to address the limitations of traditional definitions and diagnostic criteria that impede clinical practice and recommendations, ensuring that veterinary patients with obesity receive the care they deserve.
These diagnostic terms will become increasingly relevant as veterinary obesity treatments evolve. Therapeutic diets continue to become more sophisticated, and new supplements and techniques help preserve and promote lean muscle mass. Over the next decade, obesity medications will likely be approved for companion animals, making evidence-based definitions and diagnoses essential for prescriptions. Improved obesity diagnosis using artificial intelligence-assisted imaging, adipose-specific biomarkers, and emerging modalities will require us to consider defining obesity in animals “beyond the charts.”
Previous obesity classification schemes and nomenclature, such as “morbid obesity,” “Stage 1 obesity,” “metabolically healthy obesity (MHO),” or “medically unhealthy obesity (MUO),” fail to identify a clinical disease and are unwieldy. This is not to say they lack validity, but rather that they have not gained widespread acceptance. Physicians have attempted similar approaches with similarly disappointing results. It is time to explore a new path forward.
Language Begins with Simple Applications
Our initial proposal is to use “clinical obesity” to describe a patient with excess adiposity who presents with clinical signs or a concurrent obesity-associated disease diagnosis. This distinction helps differentiate between animals with a body condition score of 8 or 9 that are apparently healthy and those who are compromised and require medical intervention.
Core Definition
Clinical obesity describes a patient with excess adiposity who also presents with clinical signs or a concurrent obesity-associated disease, distinguishing animals that are compromised and need intervention from those that are apparently healthy but at risk.
As evidence for an “obesity-first medical approach” in human medicine continues to grow, this term will become more consequential. Over time, we anticipate the development of more rigorous and sophisticated diagnostic algorithms and tools to substantiate the term’s use in veterinary medicine.
For example, a cat with a BCS of 8 and hypertension, or a dog with a BCS of 9 and osteoarthritis, would be diagnosed with clinical obesity along with their comorbidities, such as “Your cat has clinical obesity and hypertension.” Treatment would focus on fat loss, lean muscle preservation, and managing the additional condition. Veterinarians better serve their patients by treating both diseases from the outset.
Obesity
Excess adiposity, such as BCS 8–9/9, without clinical signs, abnormal findings, or comorbidities. Apparently healthy, but at risk of developing obesity-associated disease.
Clinical obesity
Excess adiposity plus clinical signs or a concurrent obesity-associated disease. A compromised patient who requires medical intervention.
However, most human and veterinary patients diagnosed with both obesity and a secondary condition rarely receive early and aggressive obesity treatment. A typical recommendation is to prescribe medication for the blood pressure or pain and, at best, offer lip service regarding obesity and healthy body composition.
In human medicine, the growing evidence that addressing “obesity first” results in better outcomes is flipping the script on how physicians diagnose, treat, and discuss fat loss with their patients. I expect the same will hold true for veterinarians.
A dog with a BCS of 9 but without clinical signs, abnormal imaging or laboratory findings, or comorbidities would be diagnosed as “having obesity” and considered at risk of developing an obesity-associated disease. These patients would be prescribed a therapeutic weight-loss diet and a physical activity program. The first line of treatment for pets that are overweight or have obesity remains a therapeutic weight-loss diet, a physical activity program, and behavioral modification.
A key difference between these terms is that the current “obesity” diagnosis relies on a subjective comparison, while “clinical obesity” requires objective clinical findings.
The Power of “Clinical”
In both human and veterinary medicine, the belief is that by introducing a new obesity term using “clinical,” medical professionals and the general public will recognize it as “different” and, hopefully, as “a disease.”
As new obesity diagnostic capabilities and treatments become available, new language will be required. Veterinary medicine needs to learn from our human colleagues and begin transitioning to enhanced communication as new therapies and tests evolve.
By adding the modifier “clinical,” healthcare professionals can also distinguish “obesity” from “fatness” and other stigmatizing terms.
“Clinical” implies the need for medical assistance and guidance. Clinical obesity signifies that the condition causes clinical signs and has negative health consequences. It engages the “healthy at every size (HAES)” concept by applying it only to demonstrable disease.
In my opinion, it is unscientific to “diagnose” a two-year-old, subclinical Labrador Retriever with a disease based solely on a subjective assessment of its morphology compared to a chart drawing. While this type of subjective screening has value, does it meet the standard for a medical diagnosis?
The body mass index (BMI) has experienced similar shortcomings. Although it is a validated obesity screening tool and useful in population analyses, it is inappropriate as the sole basis for diagnosing obesity in an individual.
By adding an initial requirement of “obesity plus,” we complete the diagnosis by incorporating objective findings. In the near future, I expect advanced diagnostic testing to facilitate even earlier, more precise, and more accurate diagnoses.
A New Era of Veterinary Clinical Obesity
The next decade will be an exciting time in the diagnosis and treatment of both human and animal obesity. Veterinary medicine has the opportunity to avoid many of the mistakes human obesity medicine has encountered over the past three decades, including those related to nomenclature and communication strategies. The Lancet Commission on Clinical Obesity has recognized the need for immediate change and has worked at remarkable speed with more than 75 global organizations committed to redefining obesity medicine.
