A recent study published in The Lancet proposes two new categories to better define obesity as a health risk factor.
The Weight-Centered Focus on Obesity
Obesity definitions have traditionally focused heavily on body weight. The World Health Organization (WHO) defines obesity as “abnormal or excessive fat accumulation that may impair health.” While this definition acknowledges the potential for related diseases, it does not address the symptoms or direct harms of the condition itself. This has led many to interpret obesity more as a risk factor for other illnesses rather than a disease on its own. Moreover, the classification of obesity as a disease is deeply entangled with conflicts of interest, particularly involving pharmaceutical companies tied to weight loss treatments.
Currently, obesity classification in adults relies mainly on the Body Mass Index (BMI), which the WHO established. BMI is calculated by dividing weight (kg) by height squared (m²), with a threshold of 30 kg/m² or higher indicating obesity, regardless of sex. However, the BMI metric dates back to 1839 and was initially developed based on measurements of white men. It fails to consider critical variables like sex, age, ethnicity, or body composition. Consequently, BMI can be seen as both sexist and racist by ignoring body diversity and insisting on a single “healthy” body size linked strictly to weight and height.
Limitations of BMI and Clinical Realities
Scientific evidence from clinical practice shows BMI is a flawed diagnostic tool. Studies reveal that nearly 50% of people classified as obese by BMI are metabolically healthy, while approximately 30% of individuals with “normal weight” suffer significant health problems. Furthermore, BMI does not distinguish weight gain caused by secondary conditions such as Cushing’s syndrome or hypothyroidism, nor does it consider individual health history.
What Does The Lancet Propose?
In an effort to offer a more ethical and scientifically grounded approach, The Lancet introduces two new obesity categories:
- Preclinical Obesity: Excess fat accumulation without apparent organ damage but with potential health risks.
- Clinical Obesity: A condition in which excess adiposity affects organ function and body systems.
While the “preclinical” category frames obesity more as a risk factor, it still risks perpetuating stigma by labeling larger bodies as problematic even when metabolically healthy.
Despite emphasizing social justice and addressing weight stigma, the study remains weight-centric. Additionally, it discloses conflicts of interest due to close ties between researchers and major pharmaceutical companies such as Novo Nordisk and Eli Lilly. The guidelines recommend medical treatments like semaglutide, which in practice can lead to cycles of weight loss and regain, along with yet-unknown long-term side effects.
The Dangers of Weight Cycling
Weight cycling—repeatedly losing and regaining weight—has serious health consequences. It increases metabolic and emotional stress, raises the risk of premature death, and contributes to cardiovascular disease and diabetes.
A Call for a Size-Inclusive Health Approach
Meaningful change requires adopting a Health At Every Size (HAES) philosophy, which respects body diversity without assuming disease based solely on size. Accessible nutrition education and a preventive, rather than interventionist, public health approach are essential. Prevention can often reduce the need for pharmacological treatments.
More training on eating disorders is urgently needed. While the WHO continues to focus on obesity rates and BMI, eating disorders are rising, with cases appearing in younger children—sometimes under 12 years old.
Addressing Social and Economic Barriers
We must implement policies that ensure everyone has access to healthy food. Without this, nutritious choices risk becoming privileges only the few can afford. Social and economic factors directly impact individual health, so public health strategies must prioritize vulnerable populations.
Finally, healthcare professionals must shift away from a weight-centered mindset. Otherwise, we will continue overdiagnosing disease based on body weight and underdiagnosing conditions in people regardless of size, forgetting that no specific weight guarantees health.
About NUTRIR CON CIENCIA:
This section is dedicated to evidence-based nutrition and expert knowledge. Eating is more than a pleasure or necessity—diet and food habits are among the most powerful public health tools for preventing diseases such as cancer and diabetes. A team of dietitians and nutritionists guides us in understanding the importance of nutrition and dispelling myths that lead to poor eating habits.