Effect of Intermittent Fasting on Reproductive Hormone Levels in Females and Males: A Review of Human Trials

Summary

This Nutrients review is the first to synthesize specifically what human trials of intermittent fasting (not animal work, not religious fasting) show about sex-hormone shifts in women and men. The authors identified seven human trials total: five testing time-restricted eating, one testing a 5:2 protocol, and one studying meal timing. Their headline findings for premenopausal women with obesity: intermittent fasting reduces testosterone and the free androgen index, and increases sex hormone-binding globulin — particularly when the eating window is restricted to earlier in the day. Estrogen, luteinizing hormone, and follicle-stimulating hormone showed no statistically meaningful change in the trials reviewed. In men, intermittent fasting reduced total and free testosterone in some studies, with implications for libido and lean-mass maintenance that the authors flag as concerning at longer protocol durations. The honest summary: female reproductive hormone effects are real but modest, mostly favorable for PCOS-spectrum profiles, and depend heavily on eating-window timing.