High-Intensity Interval Training Reduces Liver Enzyme Levels and Improves MASLD-Related Biomarkers in Overweight/Obese Girls.

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• Short-term HIIT programmes may provide measurable benefits for overweight/obese adolescents, particularly in body composition and metabolic markers.

• Improvements in liver enzymes and lipids observed in this trial suggest that HIIT could play a supportive role in MASLD management.

• Structured exercise interventions in adolescence might help reduce longer-term risk of cardiometabolic complications.

Introduction

Metabolic dysfunction-associated steatotic liver disease (MASLD) is characterised by the presence of hepatic steatosis with the onset of metabolic risk factors. This study aimed to evaluate the effects of high-intensity interval training (HIIT) on selected MASLD-related biomarkers in adolescents with overweight/obesity.

Methods

This was a nine-week randomised controlled trial that enrolled thirty-six girls who were randomly assigned to the training (n = 18) or control (n = 18) groups. Girls in the control group continued their regular physical education classes but did not participate in additional training programmes.

Results

• At baseline, there were no significant differences between groups.

• Anthropometric and physical outcomes (HIIT group): Significant improvements were observed in body mass (p < .001; ES = 0.25), BMI (p = .001; ES = 0.29), body fat (p < .001; ES = 0.52), waist circumference (p = .003; ES = 0.37), and systolic blood pressure (p = .011; ES = 0.80). Maximal aerobic speed increased (p = .035; ES = 0.54) and maximal heart rate improved (p = .035; ES = 0.73). No changes occurred in the control group.

• Between-group comparisons: The HIIT group demonstrated higher maximal aerobic speed (p = .010; ES = 0.99, large effect) and lower maximal heart rate (p < .001; ES = 1.40, large effect) versus controls.

• Biochemical outcomes (HIIT group): Significant reductions occurred in total cholesterol (p = .003; ES = 0.45), triglycerides (p = .005; ES = 0.54), low-density lipoprotein cholesterol (p = .002; ES = 0.60), alanine transaminase (p = .013; ES = 0.47), aspartate aminotransferase (AST) (p = .012; ES = 0.58), and HOMA-IR (p = .010; ES = 0.47). High-density lipoprotein cholesterol increased (p = .013; ES = 0.36).

• Between-group comparisons: AST was significantly lower in the HIIT group (p = .036; ES = 0.79, moderate effect).

Conclusion

The authors concluded that a nine-week HIIT programme improves body composition and reduces liver enzymes, plasma lipids, blood pressure, and insulin resistance in over-weight/obese adolescent girls.

• HIIT can be considered as a structured, evidence-based exercise plan alongside dietary and lifestyle interventions for overweight/obese adolescents with MASLD.

• Incorporating short HIIT sessions may be more acceptable and feasible for young people compared to longer exercise regimens.

• Improvements in liver enzymes, blood pressure, lipids and insulin resistance highlight the importance of integrating physical activity into MASLD management plans.

• Further research is needed to clarify the mechanisms underlying the effects of HIIT on fatty liver while focusing on the potential direct action of muscle metabolism on the liver.

• Future research should include larger, more diverse populations and both sexes to explore gender differences.

• Studies should also control for diet and energy intake, monitor adherence to HIIT, and assess pubertal hormones that may affect outcomes.