Abstract
BACKGROUND: Phase angle (PhA), derived from bioelectrical impedance analysis (BIA), is a non-invasive parameter that reflects cellular integrity and nutritional status. Although PhA is increasingly used in pediatric settings, evidence on modifiable determinants in healthy adolescents remains limited. METHODS: This study was conducted in 56 adolescents (median age 16 years) who underwent BIA measurement including PhA at 50 kHz. Lifestyle and diet were assessed using the validated questionnaire and included physical activity level (school and free time), sleep length, and diet quality indices together with selected food intake frequencies. RESULTS: The median PhA was 5.16° (IQR 4.88-5.46). In multivariable models, male sex (B = 0.96, p < 0.001) and higher free-time physical activity were independently associated with higher PhA, with graded effects for moderate (B = 0.42, p = 0.004) and high activity (B = 0.55, p = 0.001) versus low. Dietary indices and individual food items did not retain significance after adjustment. Penalized logistic models confirmed lower odds of low PhA with moderate (OR: 0.13, 95% CI: -3.66 to -0.56) and high (OR: 0.01, 95% CI: -9.15 to -1.87) versus low free-time activity. CONCLUSIONS: In healthy adolescents, habitual free-time physical activity is the main factor of PhA. These findings support the promotion of physical activity in youth as a modifiable determinant of cellular health.