For decades, obesity has been defined through a single, dominant metric: Body Mass Index (BMI). Introduced in the 19th century and later adopted in clinical practice, BMI offered a simple way to classify populations. It became embedded in guidelines, insurance systems, and public health messaging. But simplicity came at a cost. BMI does not distinguish between muscle and fat, does not capture fat distribution, and does not reflect metabolic health. Over time, this narrow definition shaped not only diagnosis, but also how societies understand obesity itself.

Today, the field is evolving. Leading bodies such as World Health Organization and World Obesity Federation increasingly recognize obesity as a complex, chronic disease driven by biological, environmental, and social factors. There is growing emphasis on adiposity, fat distribution, metabolic risk, and long-term disease progression rather than weight alone. This shift matters because definitions are not neutral. They determine who qualifies for care, which treatments are covered, and how seriously health systems respond.

Yet, even as science advances, public discourse often lags behind. Obesity is still widely framed as a matter of personal responsibility. Language plays a central role in this. Terms such as “fat” or “obese” carry stigma in many contexts, shaping how individuals are perceived and how they perceive themselves. However, stigma is not universal in its expression. In some cultures, particularly across parts of Africa and Asia, words describing body size may not carry the same moral judgment once translated. This highlights a critical point: definitions and language must be culturally contextualized. A one-size-fits-all vocabulary risks reinforcing stigma in some settings while missing meaning in others.

Destigmatizing obesity requires more than replacing words. It demands reframing the condition entirely. Moving from blame to biology, from appearance to health, and from short-term weight loss to long-term management. When definitions evolve, they can shift systems. They influence medical training, public health priorities, and policy design.

This becomes even more urgent when viewed through the lens of equity. Access to obesity care remains deeply unequal. In high-income countries, patients may have access to comprehensive care including behavioural support, surgery, and emerging medications such as GLP-1 therapies. In many low- and middle-income countries, these options are limited or entirely unavailable. The divide is not only global but also local, shaped by income, geography, and health system capacity.

Across the Global South, obesity is rising rapidly, often alongside undernutrition. Yet policy responses remain fragmented. Medications are frequently unaffordable, prevention strategies are underfunded, and health systems are not structured for chronic disease management. Even where services exist, stigma and outdated definitions can prevent individuals from seeking or receiving care.

Bridging this gap requires more than technical solutions. It requires advocacy grounded in lived experience. Individuals who navigate these systems understand the barriers in ways that data alone cannot capture. Their voices are essential in shaping policies that are both effective and equitable.

This is where leaders like Ogweno Stephen have become increasingly influential. Drawing from personal experience with non-communicable diseases and years of community engagement through the Stowelink Foundation, his work connects grassroots realities with global policy spaces. From advancing conversations on obesity as a chronic disease to advocating for equitable access to treatment, his approach reflects a broader shift in global health. One that recognizes that solutions must be co-created with the communities they aim to serve.

As the definition of obesity continues to evolve, the stakes remain high. Definitions shape discourse. Discourse shapes policy. And policy determines who gets care. If the goal is equity, then the way we define, discuss, and respond to obesity must reflect the full complexity of the condition and the diversity of the people affected by it.