METABOLIC dysfunction-associated steatotic liver disease (MASLD), previously known as non-alcoholic fatty liver disease, affects approximately 20% of the global population, with prevalence as high as 42% in some regions, such as northern Germany. MASLD is often linked to obesity and associated conditions, including type 2 diabetes and metabolic syndrome, which can also be exacerbated by increased liver fat. Advanced stages of MASLD, such as steatohepatitis, characterised by liver injury and fibrosis, are now a leading cause of liver transplantation.
Lifestyle modifications, particularly dietary changes, have shown potential in reversing MASLD and steatohepatitis. The NutriAct trial recently explored the long-term effects of a high-protein, high-unsaturated fatty acid (UFA) diet on liver fat reduction over 12 months in middle-aged and elderly participants. The findings highlighted the benefits of increased protein and UFA intake, particularly polyunsaturated fatty acids (PUFAs), alongside reduced carbohydrate consumption. While weight loss mediated some improvements, PUFAs demonstrated a direct positive effect on liver fat, independent of weight changes.
Short-term studies have previously demonstrated similar outcomes, suggesting that macronutrient composition, particularly the balance of fats and protein, plays a crucial role in managing liver fat content. For example, PUFAs, such as omega-3, may suppress liver fat accumulation by decreasing de novo lipogenesis and enhancing thermogenesis. Increased protein intake appears to stimulate metabolic processes, including bile acid production and lipid oxidation, potentially mediated by glucagon and fibroblast growth factor 21.
Carbohydrate reduction also contributed to liver fat reduction, but the effects were largely weight loss-dependent. This reinforces the importance of overall energy balance and dietary composition. However, inconsistencies remain in the literature, particularly concerning isocaloric diets and the role of monounsaturated fatty acids, necessitating further research.
These findings suggest that personalised dietary interventions focusing on high PUFA and protein intake, alongside reduced carbohydrates, may be effective for MASLD prevention and management. Further studies are needed to clarify long-term effects and optimise macronutrient guidelines for liver health.
Katie Wright, EMJ
Reference
Pletsch-Borba L et al. Increase in PUFA and protein, and decrease in carbohydrate intake improves liver fat in 12 months and the role of weight loss as a mediator: A randomized controlled trial. Clin Nutr. 2024;43(12):361-9.
