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The role of body mass index (BMI) in defining obesity and the classification of obesity as a disease are under reevaluation, according to three new opinion papers published on July 22, 2024, in the Annals of Internal Medicine. The papers highlight varying perspectives on these issues and suggest potential unintended consequences of current definitions and approaches.
BMI: Still a Useful Tool?
In one of the papers, Adolfo G. Cuevas, PhD, and Walter C. Willett, MD, DrPH, argue that despite its imperfections, BMI remains a valuable tool for assessing adiposity at both population and clinical levels, particularly within racial and ethnic groups. They acknowledge that BMI does not distinguish between fat and lean body mass but emphasize its strong correlation with fat mass, cardiovascular risk, and mortality across diverse populations. The authors suggest incorporating weight changes since early adulthood and over time to enhance BMI’s sensitivity in assessing adiposity.
Luca Busetto, MD, supports this view, stating that while BMI has limitations, it remains a useful screening tool. However, he emphasizes the importance of also considering abdominal fat and conducting comprehensive clinical evaluations.
Defining Obesity Beyond BMI
Professor Gijs Goossens from Maastricht University Medical Center underscores the need for a more holistic approach to obesity management. He advocates for personalized therapeutic goals that address not only weight loss but also the prevention and resolution of obesity-related complications, improved quality of life, and better physical and social functioning.
Goossens, a contributor to the European Association for the Study of Obesity (EASO) framework, emphasizes that obesity diagnosis should not rely solely on BMI. He highlights the association of abdominal fat with cardiometabolic complications and warns against the risk of undertreatment for individuals with BMI below current obesity cutoffs but who still experience medical, functional, or psychological impairments.
Reframing Obesity as a Disease
In an editorial, Christina C. Wee, MD, senior deputy editor of the Annals of Internal Medicine, cautions against exclusively framing obesity as a disease. She argues that this approach might reinforce weight bias, which it aims to combat. Wee points out that focusing solely on the biological aspects of obesity while neglecting psychosocial, cultural, environmental, and behavioral contexts could hinder public health efforts.
Wee also highlights the irony in framing obesity as a disease to justify treatment coverage, which might inadvertently imply that only those with manifest disease warrant treatment. She calls for accurate risk stratification and prioritization of treatments based on individual patient needs.
Lower BMI Cutoffs for Asian Populations
Simar S. Bajaj, AB, and colleagues from Harvard University raise concerns about the lower BMI cutoffs for defining obesity in Asian populations, as suggested by the World Health Organization in 2004. They note the variability in BMI cutoffs across different Asian countries and argue that treating Asian Americans as a monolith without disaggregated cutoffs fails to account for the heterogeneity among Asian subgroups.
The authors point out that different Asian groups have varying risk levels for conditions like type 2 diabetes, questioning the appropriateness of uniform BMI thresholds. They call for professional organizations to consider these cutoffs as temporary until more sensitive and specific thresholds can be defined through further research.
Conclusion
The debate on the best way to define obesity and the role of BMI underscores the complexity of addressing this global health issue. While BMI remains a useful tool, experts advocate for a more nuanced and individualized approach to obesity diagnosis and management. Additionally, the framing of obesity as a disease and the establishment of appropriate BMI cutoffs for diverse populations require careful consideration to avoid unintended consequences and ensure equitable treatment for all individuals.
