Effect of high-intensity interval training and high-intensity resistance training on irisin and fibroblast growth factor 21 in men with overweight and obesity.

Adipose tissue browning is a physiological process that increases energy expenditure and may combat against obesity and its related risk factors. Fibroblast growth factor 21 (FGF21) and irisin, hormones affected by exercise that also affect adipose tissue browning, have not been widely studied with regard to exercise type and duration. This study compared the effect of high-intensity interval training (HIIT) and high-intensity resistance training (HIRT) on irisin and FGF21 in men living with overweight and obesity. After completing a training program three times weekly for 8 weeks, participants' serum levels of irisin and FGF21 were significantly increased in the HIIT and HIRT groups compared with the control group (p < 0.05). Additionally, body fat percentage and body weight in both training groups were significantly reduced in comparison with the control group (p < 0.05). Thus, HIIT and HIRT programs may be used as a feasible modality to promote favourable changes in body composition and irisin and FGF21, factors critical for browning white adipose tissue in men living with overweight and obesity.