By Dr. Ernie Ward, DVM · Association for Pet Obesity Prevention (APOP) and World Pet Obesity Association (WPOA)
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 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. Words such as "fat" and "obese," used as labels, judge and blame. Substitutions such as "chonky" and "fluffy" make light of a condition that shortens lives. 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 unusual among medical conditions in the emotional and social weight it carries. Many people still believe obesity results only from a lack of willpower, intentional overeating, or too little exercise, and that it can be "cured" by self-discipline alone.
Weight gain is often treated 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 framed as a failure to be a "good pet parent."
There is a grain of truth in these ideas, but they fall far short of the full picture. The causes of obesity in both humans and animals are multifactorial: genetics, hormones, environmental endocrine disruptors, the microbiome, feeding and activity patterns, life stage, neutering, medications, and more.
Like most chronic diseases, obesity results from a combination of factors. Yet we rarely blame a patient for developing cancer, kidney disease, or arthritis. We often console those affected with phrases like "It's not your fault." Why do we not approach obesity with the same compassion?
Excess body fat that has begun to harm a patient is a disease in its own right. It reduces quality of life, shortens life expectancy, and causes or complicates nearly every other medical condition. It is also an emotionally charged subject, burdened by a stigma that keeps pets from getting care.
Few diseases so urgently demand our most compassionate and precise language.
Defining Obesity in Evidence-Based Terms
For several years I have been advocating for a revision in how we define obesity in animals. The term "obesity" has become polarizing, and its definition varies widely among veterinary professionals. Relying on body condition charts alone to "diagnose" a disease is scientifically problematic.
The public and the media add to the confusion by treating obesity as an appearance or a lifestyle choice rather than a serious disease, particularly in companion animals. Phrases like "chonky cats" and "greedy dogs" are used to defuse emotion and deflect blame. They 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 published its peer-reviewed framework in January 2025 and presented it at a global online event on January 16, 2025. The Commission had announced more than a year earlier that new terminology was needed, in part because of the worldwide surge in GLP-1 medication use.
The Commission's central move was to separate two states that had been lumped together. Preclinical obesity is excess adiposity with preserved organ and tissue function. Clinical obesity is excess adiposity that has altered the function of tissues, organs, or the whole person. The authors set out to give obesity a medically coherent diagnosis and to settle the long dispute over whether obesity is a disease.
We are doing the same for veterinary medicine.
It's Time for "Clinical Obesity" in Veterinary Medicine
APOP and WPOA have advocated for the term "clinical obesity" in veterinary medicine since 2024. In 2026, WPOA published its clinical obesity framework, and APOP published the 2026 Pet Obesity Communication Guidelines (Version 2.0), which use the same terms for veterinary teams, journalists, marketers, researchers, and pet owners.
Many in organized veterinary medicine still resist the idea that pet obesity is a distinct disease, or that our current language has fallen short. Some 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 replace diagnostic criteria that impede clinical practice with criteria that support it, so that veterinary patients with obesity receive the care they deserve.
These terms will only become more important as treatment evolves. Therapeutic diets keep improving, and new supplements and techniques help preserve lean body mass during fat loss. Obesity medications will likely be approved for companion animals within the decade, and prescribing them will require an evidence-based diagnosis. Artificial intelligence-assisted imaging and adiposity-specific biomarkers will push us to define obesity in animals "beyond the charts."
Earlier classification schemes, such as "morbid obesity," "Stage 1 obesity," "metabolically healthy obesity," and "medically unhealthy obesity," never gained wide acceptance in veterinary medicine. Physicians tried similar approaches with similar results. It is time for a new path.
The Four Terms
The framework uses four terms. They are not interchangeable, and the difference between them is the difference between a finding and a diagnosis.
Overweight. Usually a body condition score (BCS) of 6 to 7 out of 9. More body fat than the ideal range, but below the usual obesity range, with no obesity-related dysfunction established by body condition alone. Weight management begins here: document the finding, review feeding, activity, weight trajectory, and muscle condition, agree on a plan, and recheck.
Obesity, used descriptively. Usually BCS 8 to 9 out of 9. Excess adiposity is confirmed, but the clinical classification has not yet been completed. This is a clinically important finding and a potential disease process, not yet a disease-stage diagnosis. It is the correct entry in the record until the assessment below is done.
Preclinical obesity. Body fat in the obesity range, with preserved function of tissues and organs after a defined, clinically appropriate assessment. The patient carries an elevated risk of progressing to clinical obesity and to other adiposity-related diseases. Preclinical does not mean healthy, low risk, or that treatment can wait. Begin structured weight management, protect muscle, and reassess.
Clinical obesity. A chronic, systemic illness in which excess adiposity in the obesity range alters the function of tissues, organs, or the whole animal, or diminishes quality of life, in an individual dog or cat. It is diagnosed with the criteria in the next section.
If the assessment is incomplete, declined, or unresolved, the record says "obesity with the stage undetermined." That is a documentation outcome, not a fifth stage, and it keeps the patient from being labeled preclinical by default.
Diagnostic Criteria for Clinical Obesity
The April version of this article proposed a simple rule: excess adiposity plus a clinical sign or a concurrent disease equals clinical obesity. That rule was a start. It was also incomplete, because it let any coexisting condition trigger the diagnosis.
The current framework sets three diagnostic criteria, and all three must be documented in the same patient. For short, we call them the Three A's.
Adiposity. Body fat in the obesity range, usually BCS 8 to 9 out of 9.
Abnormality. A clinically meaningful organ or tissue dysfunction, functional limitation, or quality-of-life impairment. A test can establish this.
Attribution. Patient-specific reasons that excess adiposity plausibly caused, worsened, or sustained the abnormality, after considering the relevant alternative explanations. A test cannot establish this on its own. A coexisting, unrelated disease is not attribution.
The third criterion, attribution, is what changed. Take the cat with a BCS of 8 and hypertension from the April version. Hypertension is an abnormality. Whether the cat has clinical obesity depends on attribution: has kidney disease or hyperthyroidism been considered and reasonably excluded, and is there a plausible line from the excess adiposity to the blood pressure? If yes, the cat has clinical obesity, and the record reads "clinical obesity and hypertension." If the hypertension is better explained by chronic kidney disease, the cat has preclinical obesity and hypertension from another cause. Both conditions are treated either way. The label tells you what is driving what.
The dog with a BCS of 9 and osteoarthritis works the same way. The difference from the April version is that the clinician now writes down why the adiposity is implicated, rather than assuming it.
A two-year-old Labrador Retriever with a BCS of 8 and nothing else wrong has preclinical obesity. That dog is treated, monitored, and rechecked. What that dog does not get is a disease diagnosis based on a comparison to a chart drawing.
What Treatment Looks Like
Treatment begins before the diagnosis is settled. For pets that are overweight or have obesity, the first line remains a therapeutic weight-loss diet, a structured physical activity program, and changes to feeding and treat habits, with regular rechecks of body condition and muscle condition.
For a patient with clinical obesity, excess adiposity is a therapeutic priority from the first visit, treated in parallel with the comorbidity rather than after it. Too many patients, human and veterinary, receive medication for the blood pressure or the pain and, at best, lip service about body composition. In human medicine, the evidence that treating obesity first improves outcomes is changing how physicians practice. I expect the same in veterinary medicine.
Success is measured in body condition, muscle condition, mobility, and quality of life, not in pounds lost.
The Power of "Clinical"
Adding "clinical" signals that the condition is causing harm and requires medical care. It separates a diagnosis from an appearance, and it separates "obesity" from "fatness" and the other stigmatizing words that have attached themselves to the condition.
It also corrects a habit that would not survive scrutiny anywhere else in medicine. The body mass index is a validated screening tool and useful in population studies, but no physician diagnoses disease in an individual from BMI alone. A body condition score deserves the same respect and the same limits. It identifies excess body fat. Whether that fat has become a disease in this patient is a separate question, answered by a documented abnormality and plausible attribution, not by the chart.
That is the whole argument in one line: excess adiposity is a finding, and clinical obesity is a diagnosis.
A New Era of Veterinary Clinical Obesity
The next decade will bring better diagnostics and, very likely, approved obesity medications for dogs and cats. Veterinary medicine has a chance to avoid the mistakes human obesity medicine made over the past three decades, including the ones about words. The Lancet Commission recognized the need for change and moved at remarkable speed, with more than 75 organizations worldwide committed to redefining obesity medicine.
The tools to make the same shift in veterinary medicine now exist. The WPOA clinical obesity framework explains how to stage a patient. The 2026 Pet Obesity Communication Guidelines explain how to talk about it, in the exam room and everywhere else. The forthcoming Wiley textbook, Veterinary Clinical Obesity: A Multidisciplinary Approach, brings the evidence together for students and practitioners.
Words matter. Let's use the right ones.
Related
- Clinical Obesity: definition and diagnostic criteria
- 2026 Pet Obesity Communication Guidelines
- Veterinary Clinical Obesity: A Multidisciplinary Approach (forthcoming)
References
- Rubino F, Cummings DE, Eckel RH, et al. Definition and diagnostic criteria of clinical obesity. Lancet Diabetes & Endocrinology. 2025;13(3):221-262. https://doi.org/10.1016/S2213-8587(24)00316-4
- Ward E. 2026 Pet Obesity Communication Guidelines. Version 2.0. Leland, NC: Association for Pet Obesity Prevention; 2026. https://doi.org/10.68316/apop.0002
- World Pet Obesity Association. Clinical obesity in dogs and cats: definition and diagnosis. https://worldpetobesity.org/clinicalobesity
