Association Between Fasting Insulin Levels and Handgrip Strength: A Cross-Sectional Study Using the Korean National Health and Nutrition Examination Survey

<b>Background</b>: Sarcopenia and metabolic dysfunction share common physiological mechanisms, and insulin resistance has been recognized as a major contributor to muscle loss. However, the independent association between circulating fasting insulin and muscle strength remains unclear. <b>Methods</b>: We analyzed data from 8343 Korean adults aged ≥ 20 years who participated in the 2015 and 2019 Korea National Health and Nutrition Examination Surveys. Multivariate outliers were removed using the Mahalanobis distance, and sampling weights were applied to account for the complex survey design. Multivariable linear regression models were constructed with progressive adjustments for demographic and metabolic covariates, and stratified analyses were conducted by age, BMI category, and diabetes status. <b>Results</b>: Crude models showed a weak positive association between fasting insulin and handgrip strength in both sexes. However, after adjustment for age and BMI, the association became significantly inverse and remained consistent in fully adjusted models. The inverse association was most pronounced in individuals aged ≤ 65 years, with BMI < 23 kg/m², and without diabetes. <b>Conclusions</b>: Elevated fasting insulin levels were independently associated with lower handgrip strength in Korean adults. These findings suggest that hyperinsulinemia may reflect early metabolic changes linked to subclinical muscle weakness, warranting further longitudinal investigation.