Background: We aimed to study the association between accelerometer-measured physical activity and metabolic markers of diabetes in a nationwide representative sample of U.S. adults. Methods: This cross-sectional analysis included 1259 adults aged ≥18 years from the 2003–2004 National Health and Nutrition Examination Survey (NHANES), the only cycle incorporating objective accelerometry. Physical activity was assessed using hip-worn accelerometers, with moderate-to-vigorous physical activity (MVPA) and sedentary time derived from validated count thresholds. Metabolic outcomes included fasting glucose, fasting insulin, glycated hemoglobin (HbA1c), and insulin resistance estimated by the Homeostatic Model Assessment (HOMA-IR). Survey-weighted linear regression models accounting for the complex sampling design were applied, with sequential adjustment for demographic, socioeconomic, anthropometric, and behavioral covariates. Sensitivity analyses tested alternative MVPA thresholds and wear-time criteria. Results: In unadjusted models, higher MVPA was inversely linked with fasting glucose and insulin concentrations; but, these associations were attenuated after full multivariable adjustment. In contrast, MVPA established a constant inverse association with insulin resistance. Higher MVPA was connected with lower HOMA-IR values, and this relationship remained statistically significant in fully adjusted models and across all sensitivity analyses (all p < 0.001). Associations between sedentary time and metabolic markers were non-sustainable after multivariable adjustment. No significant effect modification by sex was detected. Conclusions: Objectively measured moderate-to-vigorous physical activity is independently linked with lower insulin resistance in U.S. adults. These results emphasize the value of accelerometer-based assessments for identifying early metabolic risk and reinforce physical activity promotion as a key strategy for improving insulin sensitivity.
Bremer et al. (Fri,) studied this question.