Background: A new diagnostic framework for clinical obesity, proposed by the Lancet Commission, defines obesity as excess adiposity with organ dysfunction, offering a more functional assessment than traditional body mass index (BMI)-based classification. However, it has not been applied to Asian populations, where obesity-related complications arise at lower BMI thresholds. Methods: We analyzed 57,863 Korean adults aged ≥20 years from the 2014 to 2023 Korea National Health and Nutrition Examination Survey (KNHANES), a nationally representative, cross-sectional dataset. Clinical obesity was defined as excess adiposity with ≥1 obesity-related complication or functional limitation; preclinical obesity was defined as excess adiposity without complications. Age, sex, and temporal trends were examined and compared with BMI-based classifications using complex sampling weights and age-standardization. Results: The prevalence of clinical obesity and preclinical obesity was 31.2% and 8.1%, respectively. Among those with BMI-defined obesity (≥25.0 kg/m²), 20.1% had no complications, while 19.4% of overweight individuals (BMI 23.0–24.9 kg/m²) met clinical obesity criteria. Clinical obesity increased with age despite stable BMI, driven by metabolic and functional decline. Cancer prevalence was highest among individuals with clinical obesity (1.77%). Applying Western waist circumference cutoffs drastically reduced the estimated prevalence of clinical obesity to 13.1%. Longitudinal analyses showed a rising trend in clinical obesity over ime. Conclusion This is the first large-scale study to apply the clinical obesity framework in an Asian population. The framework identifies high-risk individuals missed by BMI al