Relationships between circulating irisin levels, cardiorespiratory fitness, and cardiometabolic risk: a cross-sectional study in Japanese adults

Circulating irisin levels gradually increased, and cardiometabolic risks gradually decreased with increasing cardiorespiratory fitness levels. The fitness levels required to increase irisin levels were moderate for young adults and lower than moderate for middle-aged and older adults. Moreover, circulating irisin levels are correlated with a reduction in cardiometabolic risk and an increase in cardiorespiratory fitness. These data suggest that circulating irisin levels are involved in the association between cardiorespiratory fitness and cardiometabolic risk.