Why a Uniform Obesity Disease Label Fails Individual Health Realities

Nearly one billion people worldwide live with obesity, yet applying a single, uniform 'chronic disease' label to this population would classify one in three adults in many high-income countries as having the same illness. This massive diagnostic shift aims to reduce stigma and improve access to care, but it risks ignoring the fundamental physiological differences between individuals.

The failure of BMI as a diagnostic tool

Standard medical practice relies heavily on Body Mass Index (BMI)—weight divided by height squared—to assess obesity. However, two people with the exact same BMI can have radically different health trajectories. One might suffer from heart failure, breathlessness, and limited mobility, while the other remains in excellent health throughout their life.

Because current medical models often tie treatment access to comorbidities, people living with excess weight are frequently denied care unless they can demonstrate established organ dysfunction. This approach treats obesity as a population-level statistical risk rather than a personalized medical condition, a move that contradicts how most other diseases are diagnosed in modern medicine.

Distinguishing preclinical from clinical obesity

In January 2025, an international commission of 56 global experts convened by The Lancet Diabetes & Endocrinology concluded that a uniform disease label is incompatible with the varied manifestations of obesity. To resolve this, the commission proposed a critical distinction between two states:

1. Clinical obesity: The presence of excess fat tissue that directly impairs daily activities or causes demonstrable organ dysfunction, such as metabolic dysfunction or breathing disorders. This state is unequivocally a disease.
2. Preclinical obesity: A condition of increased body weight and excess fat where organ function remains preserved. In this state, risk is elevated, but established disease is absent.

Crucially, both categories are defined independently of coexisting conditions like type 2 diabetes or cancer. This distinction allows clinicians to treat risk as risk and disease as disease, preventing the medical system from over-pathologizing individuals who do not yet show signs of physiological impairment.

Navigating the controversy of diagnostic thresholds

Despite endorsement from 76 medical organizations, the framework faces pushback from specialists who argue that demonstrating exactly when excess fat causes organ dysfunction is an impractical diagnostic hurdle. Critics worry that a 'preclinical' category might restrict access to weight-loss drugs and specialist follow-up for those who need them most.

However, the push for a universal disease label often stems from population-level observational data—such as the 'ideal weight' tables developed by the Metropolitan Life Insurance Company in the 1940s—which link excess weight to increased mortality. While these statistical associations are real, they do not account for the individual variability that defines clinical medicine. Moving toward a nuanced model of clinical and preclinical obesity provides a more accurate foundation for policy, insurance, and personalized patient care.

Source: Obesity doesn't equate to ill health: why the 'disease' label doesn't always fit
Domain: nature.com