why the 'disease' label doesn't always fit

Nearly one billion people worldwide live with obesity, yet the global scientific community remains deeply divided over how to define the condition. For decades, obesity was viewed primarily as a health risk that increased the likelihood of premature death, cardiovascular disease and diabetes.

Recently, there has been a push to describe obesity as a chronic disease. This shift aims to reduce social stigma and improve access to medical care for those who have long been denied it.

A New Framework for Diagnosis

In January 2025, an international commission of 56 global experts, convened by The Lancet Diabetes & Endocrinology in June 2022, reached a significant conclusion. The group determined that a single, uniform disease label is incompatible with the varied ways obesity manifests in individuals.

To address this, the commission proposed a distinction between clinical and preclinical obesity. This framework seeks to treat risk as risk and disease as disease.

Did You Know? The classical medical scholar Hippocrates noted that “corpulence” could signal future illness in some people, constitute a disease in others, and even protect some individuals from other maladies.

Clinical vs. Preclinical Obesity

Clinical obesity is defined as the presence of excess fat tissue that directly causes demonstrable organ dysfunction or impairs daily activities. Examples include limited mobility, breathing disorders, heart failure, and metabolic dysfunction.

Preclinical obesity describes a state of increased body weight and excess fat where organ function remains preserved. While the risk of future issues is elevated, it is not considered an established disease.

Both categories are defined independently of other conditions, such as mental-health disorders, cancer, or type 2 diabetes, which may coexist with either state.

The Limitations of BMI

The current standard for assessing obesity is the body mass index (BMI), calculated by dividing weight by height squared. However, experts argue that BMI is flawed because individuals with the same BMI can have radically different health trajectories.

One person with a BMI of 35 might remain in good health throughout their life, while another with the same score might struggle with severe organ dysfunction. BMI cannot predict an individual’s prognosis or their response to treatment.

Expert Insight: Samantha Carter notes that the tension here lies between population-level data and individual patient care. While statistics show that obesity increases risk across a population, applying a blanket “disease” label to every individual may oversimplify a complex biological reality and distort clinical foundations.

The Scientific Debate

The commission’s framework has been endorsed by 76 medical organizations but faces pushback from other specialists. Critics argue that demonstrating that excess fat directly causes organ dysfunction creates an impractical diagnostic threshold.

Obesity- Diagnosis and Treatment

Some worry that the “preclinical” category could lead to restricted treatment access for certain patients. They contend that comorbidities, such as type 2 diabetes, should be included in the diagnosis of clinical obesity.

there is no single unifying biological basis for all obesity. While rare genetic mutations like leptin deficiency exist, most people with obesity have a constellation of gene variants that predict a risk of excess fat, but not necessarily clinical disease.

The Role of Modern Medication

The efficacy of GLP-1 receptor agonists is often cited as evidence that obesity is a disease. However, proponents of the nuanced view argue these drugs show that body weight is biologically modifiable, not that obesity is uniformly a disease.

Unlike treatments for type 1 diabetes, which correct a pathological defect, GLP-1 drugs modulate appetite and satiety pathways shared by most people. Increased body fat may be a regulated physiological response to environmental pressures, such as ageing or ultra-processed foods, rather than an intrinsically pathological process.

Potential Implications

The ongoing division over how to diagnose obesity could impact several sectors of healthcare. If a uniform disease label were adopted, one in three adults in many high-income countries could be classified as having the same chronic illness.

Such a shift may lead to a scenario where a vast number of people are entitled to lifelong treatments, including bariatric surgery and weight-loss drugs. Conversely, the proposed distinction between clinical and preclinical states could lead to more targeted care based on actual organ dysfunction.

these diagnostic decisions may influence future insurance policies, public-health decisions, and the way clinical care is delivered to patients.

Frequently Asked Questions

What is the difference between clinical and preclinical obesity? Clinical obesity involves excess fat tissue that directly causes organ dysfunction or impairs daily activities. Preclinical obesity involves increased body weight and excess fat, but organ function remains preserved. Why is BMI considered an insufficient measure of health? BMI only measures weight relative to height and cannot predict an individual’s clinical status, prognosis, or biological underpinnings. People with the same BMI can have vastly different health outcomes. Do all people with obesity share the same genetic cause? No. There are no known genetic abnormalities shared across all people with obesity. While some rare disorders involve specific gene mutations, most cases involve a variety of gene variants that predict risk rather than a guaranteed disease state. Do you believe medical diagnoses should be based on population-level risks or individual organ function?

why the ‘disease’ label doesn’t always fit