BACKGROUND: Fibroblast growth factor 21 (FGF21) is a metabolic regulator that may promote glucose and energy homeostasis. Circulating levels of FGF21 have been shown to increase following an acute bout of exercise; however, the effect of biological sex and exercise modality remains understudied.
PURPOSE: This study was undertaken to determine if changes to FGF21 post-exercise are dependent on biological sex and exercise modality.
METHODS: Following a randomized crossover design, fifteen male and fifteen female participants completed two, thirty-minute exercise protocols. During the steady state (SS) protocol, participants cycled at 70% of VO2peak and during the sprint interval exercise (IE) protocol participants completed six, 30 second “all out” sprints against 7.5% of body weight with 4.5 minutes of active recovery between sprints. Blood samples were taken at baseline, immediately post-exercise (IPE), and 1-hour post-exercise. Oxygen consumption was monitored continuously throughout the trials. The FGF21 incremental area under the curve (iAUC) was calculated for each condition. iAUC values violated normality and were compared using appropriate non-parametric tests.
RESULTS: Comparison of the post-exercise FGF21 iAUC between categories of biological sex revealed that in the SS condition males (1336 ± 458 pg/mL) had a significantly greater FGF21 response than females (434 ± 360 pg/mL) (U = 46.0, p = 0.04). During the IE condition males (468 ± 425 pg/mL) had a greater FGF21 response than females (8 ± 153 pg/mL), but this difference was not significant (U = 53.0, p = 0.14). When comparing exercise modalities, the SS condition produced a greater FGF21 response in both sexes compared to IE. For males, this difference was significant (Z = -2.3, p = 0.02). For females there were no significant differences between exercise conditions (Z = -1.22, p = 0.22).
CONCLUSION: Exercise significantly increased FGF21 levels in males, but not in females. In males, FGF21 levels were greater in the SS condition than in the IE condition.