Reference values for adiposity indices and their associations with sarcopenic obesity in Korean adults: findings from the KNHANES database

Background Adiposity is a major risk factor of chronic diseases. Various adiposity indices have been suggested to assess adiposity; however, sex- and age-specific reference values for Korean adults are currently unavailable. Methods and results We analyzed 2022–2023 Korea National Health and Nutrition Examination Survey data concerning 10,690 adults aged 19–80 years (4,675 men; 6,015 women). The adiposity indices included the body shape index (ABSI), body mass index (BMI), conicity index (ConI), waist-corrected BMI (wBMI), waist-to-height ratio (WHtR), and weight-adjusted waist index (WWI). Sex- and age-specific reference values were derived using the lambda-mu-sigma method. Associations with sarcopenic obesity were estimated using logistic regression analysis. Receiver operating characteristic curve analysis provided area under the curve (AUC) and optimal cut-off values. Results ABSI, ConI, and WWI increased consistently with advancing age in both sexes, whereas the other indices showed sex-specific patterns. In men, BMI and wBMI increased throughout midlife and then decreased; in women, both BMI and wBMI increased with age. Among the older adults, WWI showed the highest predictive performance for sarcopenic obesity (AUC: men, 0.78; women, 0.69). WWI also exhibited the strongest association (odds ratio [OR] 3.62, 95% confidence interval [CI] 2.46–5.33). By contrast, BMI (OR 0.26, 95% CI 0.15–0.43) and wBMI (OR 0.33, 95% CI 0.21–0.54) showed inverse associations with sarcopenic obesity. Conclusions Sex- and age-specific reference values were established for six adiposity indices. ABSI, ConI, and WWI increased with age in both sexes. The WWI best identified sarcopenic obesity in older adults.