Development and Preliminary Psychometric Evaluation of the Exercise and Nutrition Consistency Scale (ExNCS): A Cross-Sectional Study of Perceived Exercise-Nutrition Integration in Young, Physically Active Turkish Adults

Abstract

Background: Instruments assessing physical activity and diet usually measure each behavior separately or sum them as independent lifestyle components. This cross-sectional study developed the Exercise and Nutrition Consistency Scale (ExNCS), a Turkish self-report measure of perceived exercise-nutrition integration, and reports a preliminary psychometric evaluation. Methods: Adults who exercised at least weekly (N = 583; 58.7% male; 93.7% aged 18–25) completed 20 expert-reviewed items. Using a seed-documented split, item screening and exploratory analyses used the development half (n = 291), and six measurement models were compared in the holdout half (n = 292) using robust maximum-likelihood and ordinal (WLSMV) estimation. Results: Four reverse-worded items were removed, leaving 16 items. Retention criteria disagreed (two versus four factors), and no model met conventional WLSMV fit criteria (best: correlated four-factor, CFI = 0.865, RMSEA = 0.122). The symmetrical bifactor model was inadmissible; a bifactor-(S-1) model, estimated despite poor fit, indicated a strong general dimension (ECV = 0.73; ω_h = 0.88) that is best read as an exploratory composite rather than a confirmed construct. Total-score α was 0.913, scores increased with exercise frequency (η2 = 0.153, 95% CI 0.102–0.204), sex invariance was inconclusive, and acquiescence was detected. Conclusions: The ExNCS is a candidate item set, but its dimensional structure and score interpretation require independent replication.