By Dr Mohgah Elsheikh: Obesity is a complex condition linked to numerous common diseases, including type 2 diabetes, heart disease, fatty liver disease and osteoarthritis. For years, healthcare professionals have defined obesity using Body Mass Index (BMI), calculated by dividing a person’s weight (in kilograms) by the square of their height (in metres). For individuals of European descent, a BMI of 30 kg/m² or higher indicates obesity.
What are the Limitations of BMI?
While BMI is widely used, it has significant limitations. It does not differentiate between fat and muscle mass or indicate how fat is distributed in the body. This can lead to misclassifications:
The Lancet Commission’s New Approach to Defining Obesity
The Lancet Commission, comprising 56 experts (including individuals with lived experience), has proposed a more comprehensive way to define obesity. Instead of solely relying on BMI, they recommend incorporating additional measurements, such as:
These tools aim to confirm the presence of excess or unhealthy fat distribution, offering a more accurate diagnosis.
The New Definition: Two Categories of Obesity
The Commission introduces two categories to better reflect the health impacts of excess body fat:
By distinguishing between these categories, the Commission hopes to personalise treatment, ensuring interventions are tailored to individual needs and that resources are allocated effectively.
Concerns About the New Definitions
While the new approach has merits, it has raised some concerns:
1. What is “Excess” Body Fat?
The Commission does not provide a precise definition of “excess” body fat. Current criteria rely on population studies rather than individual health assessments, making it difficult to standardise the term.
2. Confusing Terminology
The distinction between “comorbidities” (conditions that coexist with obesity) and “complications” (conditions caused by it) is unclear. For example type 2 diabetes is considered a separate condition, while polycystic ovary syndrome (PCOS) is viewed as part of obesity. This inconsistency can complicate diagnosis and treatment.
3. Overcomplicated Diagnoses
The European Association for the Study of Obesity (EASO) has expressed concerns that the new classification of pre-clinical obesity could delay early interventions, potentially worsening long-term health outcomes.
4. Mental Health Overlooked
Mental health, often closely linked to obesity as both a cause and consequence, is notably absent from the report’s considerations.
5. Adding Complexity Without Benefit
Some experts argue that existing frameworks, such as the Canadian guidelines or the EASO model, already define obesity as a condition that impairs health rather than solely relying on BMI. The new definitions may add unnecessary complexity without clear benefits.
Conclusion
The Lancet Commission’s recommendations mark a significant shift in how obesity is viewed and diagnosed. By recognising it as a disease with varying stages and effects, the Commission aims to reshape perceptions and guide future healthcare strategies.
However, the new definitions are not without challenges. The lack of clarity around “excess” body fat, the potential for delayed interventions, and the absence of mental health considerations highlight areas for improvement.
Obesity is a chronic disease that requires a holistic, personalised approach to management. By focusing on early intervention and comprehensive care, we can address the health challenges obesity presents and improve outcomes for those affected.