Effects of Intermittent Fasting on Male and Female Reproductive Hormones, Fertility, and Sexual Function: A Comprehensive Review with Emphasis on the Existing Evidence Gap in Women.

Intermittent fasting (IF) has emerged as a popular dietary intervention with potential metabolic and endocrine benefits. However, its effects on sexual function and reproductive health remain incompletely understood. This comprehensive review synthesizes current evidence from human clinical trials and animal studies examining the impact of various IF protocols-including time-restricted eating (TRE), alternate-day fasting (ADF), and Ramadan fasting-on male and female sexual function, reproductive hormones, and fertility outcomes. In males, limited human data suggest preserved erectile function but reduced sexual desire during Ramadan fasting, with neutral effects on testosterone in obese adults undergoing TRE. Animal studies demonstrate context-dependent effects, with IF protecting against high-fat diet-induced reproductive dysfunction while potentially impairing spermatogenesis under prolonged energy restriction. In females, IF shows promise for improving hyperandrogenism and menstrual regularity in polycystic ovary syndrome (PCOS), mediated by enhanced insulin sensitivity and reduced free androgen index. However, direct measurements of female sexual function domains (libido, arousal, lubrication, orgasm) are largely absent from the literature. Mechanistic pathways involve modulation of the hypothalamic-pituitary-gonadal (HPG) axis, insulin-adipokine signaling, sex hormone-binding globulin (SHBG), and oxidative stress pathways. Evidence quality is limited by small sample sizes, heterogeneous protocols, short follow-up periods, and predominance of animal data. While IF may offer reproductive benefits in metabolically compromised populations, particularly women with PCOS, caution is warranted in young, lean, or energy-deficient individuals. Future research should employ standardized IF protocols, validated sexual function instruments, and long-term fertility endpoints to establish evidence-based clinical recommendations.