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

Abstract

Intermittent fasting is a popular diet for weight loss, but concerns have been raised regarding the effects of fasting on the reproductive health of women and men. Accordingly, we conducted this literature review to clarify the effects of fasting on reproductive hormone levels in humans. Our results suggest that intermittent fasting decreases androgen markers (i.e., testosterone and the free androgen index (FAI)) while increasing sex hormone-binding globulin (SHBG) levels in premenopausal females with obesity. This effect was more likely to occur when food consumption was confined to earlier in the day (eating all food before 4 pm). In contrast, fasting did not have any effect on estrogen, gonadotropins, or prolactin levels in women. As for men, intermittent fasting reduced testosterone levels in lean, physically active, young males, but it did not affect SHBG concentrations. Interestingly, muscle mass and muscular strength were not negatively affected by these reductions in testosterone. In interpreting these findings, it is important to note that very few studies have been conducted on this topic. Thus, it is difficult to draw solid conclusions at present. From the limited data presented here, it is possible that intermittent fasting may decrease androgen markers in both genders. If this is the case, these results would have varied health implications. On the one hand, fasting may prove to be a valuable tool for treating hyperandrogenism in females with polycystic ovarian syndrome (PCOS) by improving menstruation and fertility. On the other hand, fasting may be shown to decrease androgens among males, which could negatively affect metabolic health and libido. More research is warranted to confirm these preliminary findings.

Impact of nutritional diet therapy on premenstrual syndrome

“…Research has shown that short-term intermittent fasting can lead to more excellent parasympathetic activity and lower luteal cortisol levels in young women. These results indicate the possibility of producing an anti-stress effect in the luteal phase, which would reduce menstrual symptoms ( 34 , 35 ).…”

Ramadan intermittent fasting reduces visceral fat and improves gastrointestinal motility

“…31 A recent review focusing on the effects of intermittent fasting on reproductive hormone levels reported the lack of significant effects of fasting on oestrogen, gonadotropins or prolactin levels in women. 32 Further studies must address the potential relationships between intermittent fasting, body fat distribution and sex hormones in healthy and unhealthy women.…”

Intermittent fasting and time-restricted eating role in dietary interventions and precision nutrition

“…Studies have shown that IF and TRE have cardiometabolic benefits aligned with the circadian rhythm, independent of their weight loss outcomes. In a symposium review ( 58 ), Cienfuegos and colleagues attributed the cardiometabolic benefits of TRE to circadian rhythm and biological clocks, which affected glucose regulation, beta cell responsiveness, body composition, and body composition body weight, reduction of oxidative stress and metabolic switch ( 24 , 59 – 62 ). As such, since fasting deprives the body of glucose, and after glycogen stores are depleted (within 12 h of fasting), the energy production is shifted to alternative energy sources such as fatty acids and ketone bodies, leading to the metabolic switch flipping ( 63 ).…”