Effects of Resistance Exercise and Whey Protein Supplementation on Irisin Levels in Patients with MASLD Under a...

Objectives: The aim of this study was to explore the combined effects of resistance exercise and whey protein supplementation on plasma irisin levels in patients with metabolic dysfunction-associated steatotic liver disease (MASLD) under a 30% calorie-restricted weight loss diet. Methods: Thirty adult patients with MASLD were randomized into the following three groups for a 4-week intervention: calorie restriction group (CR) (n = 8), CR with resistance exercise group (EX) (n = 11), and CR with resistance exercise and whey protein group (EX + P) (n = 11; 0.7 g/kg per day). All participants received boxed meals providing 70% of their total energy expenditure. The participants in the resistance exercise groups performed full-body resistance exercises 5 days/week (50-75% one-repetition maximum). Plasma irisin level, controlled attenuation parameter (CAP), and body composition were assessed before and after the intervention. Results: Plasma irisin levels significantly increased in the EX (+2.24 ng/mL, p = 0.016) and EX + P (+4.86 ng/mL, p = 0.004) groups but not in the CR group. Muscle mass increased significantly only in the EX + P group. The CAP decreased in all groups. The change in irisin level was negatively correlated with the change in CAP (r = -0.459, p = 0.032). Conclusions: Resistance exercise under calorie-restricted conditions effectively increased plasma irisin levels in patients with MASLD, whereas caloric restriction alone did not. Furthermore, a stronger increasing trend in the plasma irisin levels was observed with whey protein supplementation. An increase in irisin levels was significantly associated with hepatic fat reduction, suggesting that irisin may serve as a biomarker reflecting improvements in hepatic steatosis following lifestyle intervention.