Intermittent fasting is a term for three different diet regimes. Alternate day fasting involves a feast day where individuals can eat what they want followed by a water only day. The 5:2 diet involves 5 feast days and 2 fast days per week. Time-restricted eating (TRE) involves a short eating window of a specific number of hours per day. Although these are all popular diet regimes for weight loss, animal studies have highlighted concerns with regards to reproductive health. This review paper aimed to summarise the human research on the effects of intermittent fasting on reproductive hormone levels in both men and women. It was found that overall, there were very few studies, however evidence was found on the effect of intermittent fasting on some of the sex hormones. For women, moving calorie intake to earlier in the day may be of benefit to oestrogen, sex hormone binding globulin, and androgen levels in those with polycystic ovary syndrome (PCOS). In addition, a fasting diet may be of benefit to androgen and SHBG levels in women with PCOS. However even though weight loss may be achieved with intermittent fasting, this is insufficient to improve the gonadotrophins. Intermittent fasting was found to be safe in women who were breastfeeding, with no significant change to milk production. In men, TRE was found to negatively affect testosterone levels, but had no effect on SHBG. The effect of intermittent fasting on sex hormones may involve changes in the gut microbiome and circadian rhythms as a direct result of intermittent fasting. It was concluded that the sex hormone levels of women with PCOS may benefit from intermittent fasting, however in men it may be detrimental to sex hormone production. This study could be used by healthcare professionals to understand that recommending an intermittent fasting diet may be of benefit to hormone levels and fertility in women with PCOS, however this may not be the case for men.