Effects of short‐term supervised exercise training on liver fat in adolescents with obesity: a randomized controlled trial

Abstract Objective The objective of this study was to quantify the effects of a 4‐week, supervised, high‐intensity interval training (HIIT) on intrahepatic triglyceride content (IHTG, percentage), cardiorespiratory fitness (CRF), and cardiometabolic markers in adolescents with obesity. Methods A total of 40 adolescents (age 13–18 y, BMI 36.7 ± 5.8 kg/m 2 ) at risk for metabolic dysfunction‐associated steatotic liver disease (MASLD) based on obesity and elevated Fibroscan measured controlled attenuation parameter (CAP) scores were randomized to HIIT three times a week for 4 weeks ( n = 34) or observation (control; n = 6). Liver magnetic resonance imaging proton‐density fat‐fraction (MRI‐PDFF), CAP, oral glucose tolerance test, serum alanine aminotransferase, dual‐energy x‐ray absorptiometry, and CRF tests were performed before and after intervention. Within‐ and between‐group differences were compared. Results A total of 13 (38%) and 4 (66%) children had MASLD by MRI‐PDFF (IHTG ≥ 5%) in the HIIT and control groups, respectively. The implemented HIIT protocol had no impact on CRF or IHTG (baseline 5.26%, Δ = −0.31 percentage points, 95% CI: −0.77 to 0.15; p = 0.179), but it decreased the 2‐h glucose concentration (baseline 116 mg/dL, Δ = −11 mg/dL; 95% CI: −17.6 to −5.5; p < 0.001). When limiting the analysis to participants with MASLD ( n = 17), HIIT decreased IHTG (baseline 8.81%, Δ = −1.05 percentage points, 95% CI: −2.08 to −0.01; p = 0.048). Between‐group comparisons were not different. Conclusions The implemented exercise protocol did not reduce IHTG, but it led to modest improvement in markers of cardiometabolic health.