Total body potassium and body cell mass in adolescents with obesity

Body composition abnormalities are associated with adverse health outcomes, but assessing them in adolescents with obesity is challenging because growth and obesity alter tissue hydration. This exploratory study (1) examined relationships between body cell mass (BCM), derived from hydration-independent total body potassium (TBK), and anthropometry, body composition, and muscle strength, and (2) evaluated agreement between measured and predicted TBK.

Twelve adolescents with obesity (median age: 12.8 years; 75% females; median BMI z-score 2.5) underwent TBK assessment using a whole-body potassium counter, alongside anthropometry, air-displacement plethysmography, bioelectrical impedance analysis, ultrasound, and handgrip strength assessments.

BCM positively correlated with age, height, weight, fat-free mass, and handgrip strength (r = 0.70-0.90; p ≤ 0.015), but not significantly with fat mass, muscle thickness and cross-sectional area, subcutaneous adipose tissue thickness, or phase angle. Predicted TBK using age- and sex-based equations [median (IQR): 81.7 g (74.6, 85.0)] was lower than measured TBK [92.7 g (74.2, 98.2)], with a median difference of 9.2% (p = 0.012).

BCM was positively correlated with age, body size, fat-free mass, and muscle strength in adolescents with obesity. Predicted TBK was lower than measured TBK; however, the small, predominantly female sample precluded adequate consideration of sex, sexual maturation, and other potential confounding factors, limiting interpretation of this discrepancy. These preliminary findings should therefore be interpreted with caution and confirmed in larger, more diverse cohorts.