Don’t Chase a Number on a Scale: Transcending Weight in Animal Obesity Research and Care

Body weight is a poor individual indicator of overall health and disease risk. 

Obesity is a disease, not a social construct.

For decades, those two statements have caused confusion and controversy within the human and veterinary medical professions. Research into health outcomes has shown that excessive emphasis on body weight, particularly when applied to calculations of weight and height (Body Mass Index or BMI), can lead to potential misinterpretation of results and incomplete conclusions. Defining obesity in terms of volition and choice undermines the multitude of physiological causes for the disease. 

While BMI, weight, and descriptive terms are essential elements of medical practice, there continues to be an exaggerated emphasis by many human and veterinary professionals on weight as a sole measure of risk and outcome. 

The approval of several effective human weight loss medications, notably the GLP-1 agonists, has intensified the debate on obesity’s causation, appropriate terminology, and the impact of weight loss on overall well-being.

Yet, we continue to chase a number on a scale. Those numbers can potentially divide and stigmatize those affected, both human and animal, despite demonstrable improvements in health independent of weight.

We can do better.

1. Weight Matters in Context

Body weight has tremendous utility when used as a marker of risk, not a cause. Veterinarians must continue to use body weight in conjunction with other measurements, including body condition score( BCS) and muscle condition score (BCS), along with traditional biomarkers of disease and symptomology. 

An animal's weight can not serve as a surrogate for health status. In other words, a “normal” weight measurement may be misleading in terms of excess adiposity, while an “overweight” animal may have a healthy amount of body fat. 

Be sure to incorporate and evaluate body weight as one data point in a complete set, including BCS, MCS, images, ambulation and gait, quality of life, and other body condition and health metrics.

2. Health Outcomes May Exceed the Amount of Weight Gain or Loss

Veterinarians understand that a lab test result is often merely one facet of a successful diagnostic or treatment plan. Patient outcomes are usually measured by mitigating clinical signs and improving quality of life and are not solely reliant on changing lab values. In other words, just because a test says a patient is better doesn’t make them well, and vice versa.

A decrease in body weight may be due to many reasons and affects a broad spectrum of physiological processes. Even seemingly negligible weight loss can be significant in terms of improved health and quality of life. The positive health impacts are potentially more important when a weight reduction reflects predominantly fat loss. When weight loss comes at the expense of lean muscle mass or hydration, overall health may be decreased. 

It is critical to view the success or failure of a “weight loss program” in terms of improved health and quality of life. Tracking biomarkers, activity, and comfort are all foundational when evaluating health outcomes for obesity patients. Victory or defeat in health is more than measuring pounds gained or lost.  

3. The Need for Advanced Veterinary Obesity Science

Obesity is a chronic disease, and any chronic condition is complicated to treat. Obesity in animals lags behind human obesity science. Economics and scale are partly to blame for a lack of approved treatments and tests, but there is much available. Veterinarians need to incorporate the preponderance of animal obesity research and resources currently available. Animal nutritional science has progressed steadily over the past hundred years, and today’s therapeutic diets, ingredients, formulations, lab tests, and strategies are backed by extensive research. We’ve progressed far beyond “Feed less.” and now have a variety of evidence-based feeding tactics developed by decades of rigorous science.

The advances in human anti-obesity medications (AOMs) and biomarkers to detect health risks will soon arrive in veterinary medicine. As humans with obesity see dramatic health and quality of life improvements, the demand for similar treatments for their animals will follow. Veterinarians and companies must embrace a multidisciplinary approach to obesity care, including diagnostic testing, diet, behavioral, and medical interventions in conjunction with co-morbidity treatments.

Obesity is a disease. Health risk is more than body weight. Veterinarians should expand beyond relying solely on changes in body weight as a single indicator of health or a measure of outcome success.

Stop chasing a number on a scale and focus on healthy body condition, adiposity, and quality of life.