Self-Directed High-Intensity Interval Versus Moderate Continuous Training on Cardiometabolic Health in Metabolic...

Exercise is recommended for metabolic dysfunction-associated steatotic liver disease (MASLD, previously known as nonalcoholic fatty liver disease [NAFLD]), but the optimal exercise mode remains unclear. We compared high-intensity interval training (HIIT) versus moderate-intensity continuous training (MCT) on cardiorespiratory fitness in patients with MASLD. This randomized trial assigned patients with ultrasonography-confirmed NAFLD/MASLD to HIIT (n = 46) or MCT (n = 49) for 24 weeks; a non-randomized observation group (OBS; n = 20) was also recruited. Both exercise groups performed self-directed treadmill training thrice weekly in free-living settings (home, residential gyms, or community fitness facilities). HIIT: 5 cycles of 4-min intervals at 80%-90% peak oxygen consumption (V̇O_2peak) with 3-min recovery at 50% V̇O_2peak. MCT: 30-40 min at 60% V̇O_2peak. Outcomes were assessed at baseline and week 24. Both HIIT and MCT significantly reduced hepatic steatosis versus OBS (both p < 0.05), with no between-group difference. HIIT achieved greater V̇O_2peak improvements than MCT and OBS (p < 0.05). Both exercise groups increased minute ventilation and carbohydrate utilization at moderate-to-high intensities versus OBS (p < 0.05). HIIT and MCT equally reduce hepatic steatosis in patients with MASLD, suggesting exercise participation matters more than intensity for liver fat reduction. Importantly, HIIT provides superior cardiorespiratory benefits. Trial Registration: ClinicalTrials.gov (NCT04463667).