Advantages and Critical Reappraisal of New Clinical Obesity Definition Proposed by Lancet Commission

Commission proposed a disease-oriented redefinition of obesity, distinguishing clinical obesity-excess adiposity causing organ dysfunction or functional impairment-from preclinical obesity, characterized by excess adiposity without established dysfunction. This shift has important implications for diagnosis, epidemiology, and health policy. In this review, we critically appraise the conceptual framework, emerging evidence, and implementation challenges of the new Lancet Commission definition of clinical obesity. Population-based studies from diverse regions consistently demonstrate marked discordance between BMI-defined and clinical obesity, with clinical obesity showing stronger associations with cardiometabolic disease, mortality, functional limitation, and cancer risk. These findings highlight the limitations of universal BMI thresholds, particularly in Asian populations with a predisposition to visceral adiposity at lower BMI levels. We compare the Lancet Commission framework with existing staging systems, including the Edmonton Obesity Staging System and the European Association for the Study of Obesity framework, and identify key challenges related to causal attribution, binary classification, scalability, and ethnic adaptation. Finally, we propose a refined, population-sensitive and pragmatic approach that conceptualizes preclinical and clinical obesity as stages along a trajectory, incorporates ethnicity-adapted adiposity thresholds, and emphasizes readily available clinical criteria for determining dysfunction and disease. The resulting definition of clinical obesity should support more precise and equitable obesity care.