Does Metabolically Healthy Obesity Really Exist: Going Toward New Definitions

CONTEXT: Obesity is a heterogeneous chronic disease traditionally defined by body mass index, yet individuals with similar body mass index values can exhibit substantial variability in the presence of cardiometabolic risk factors independent of adiposity. Such discordance has led to the concept of "metabolically healthy obesity", describing individuals with excess adiposity but without overt metabolic abnormalities. However, the validity and clinical relevance of metabolically healthy obesity remain controversial. EVIDENCE ACQUISITION: We conducted a narrative review of PubMed-indexed studies examining obesity phenotypes considering the recent preclinical/clinical obesity framework proposed by the Lancet Commission on Diabetes and Endocrinology. Preference was given for large epidemiological cohorts and mechanistic studies with detailed phenotyping. EVIDENCE SYNTHESIS: The metabolically healthy obesity concept is limited by inconsistent definitions, reliance on cardiometabolic risk factors, and poor long-term stability. Emerging evidence supports a shift toward a disease-based framework distinguishing preclinical obesity (excess adiposity with preserved organ and tissue function) from clinical obesity which is associated with organ dysfunction. CONCLUSIONS: Replacing binary metabolic phenotypes with the preclinical and clinical obesity framework proposed by the Lancet Commission provides a biologically grounded, clinically actionable model that aligns obesity classification with organ dysfunction and disease progression. Adopting a continuum-based, function-oriented approach may improve risk stratification, guide therapeutic prioritization, and reduce misconceptions surrounding "benign" obesity.