If you’re trying to get pregnant, or just hope to be one day and you’re worried that intermittent fasting might affect your level of fertility, research shows that it has no negative effects at all, and in some cases even improves your fertility levels.
There has been research in several animal species which show a decrease in reproductive hormones when fasting just prior to ovulation however these results have depended on the species and the nutritional status of the animal at the time.
This isn’t likely to happen to us because if we’re ifasting properly (and eating well on non fasting days/parts of the day) we’ll be well nourished from our meals. It’s actually the chronic dieters who restrict calories and are poorly nourished that have problems conceiving.
The studies that show decreased fertility levels in rats and mice are pretty much irrelevant to humans because they are ‘foragers’ compared to us hunter-gatherers. Any period of time that a species who forage for food (and therefore rarely go without it) is likely to trigger a decrease in reproduction hormones as the message their body is receiving is that ‘food is scarce’. Throughout the Paleolithic era (the majority of the time humans have been on earth) we ate intermittently naturally, when we could find and hunt for food.
A recent study in human females in the International Journal of Fertility and Sterility (2010) looked at the effect of intermittent fasting on ovulation and fertility hormones such as follicle stimulating hormone, estradiol and progesterone, in 24 women with normal menstrual cycles. They found that there were no changes in these hormones when fasting compared with not fasting, and no changes at all in ovulation.
Another study in the ‘Reviews of Reproduction’ Journal (1996) showed that females who fasted intermittently for short durations were actually more fertile in the follicular phase of menstruation (days 1 to 4 of their period) and from day 14 (at ovulation) until day 28 they showed slightly and insignificantly less, reproductive hormones during each fast. However as soon as they ate again after the fast these hormones normalized. It concluded there was no evidence of a decrease of reproductive hormone and fertility due to short-term fasting.
So you can rest assured that your fertility levels won’t be affected by intermittent fasting, but if you’re trying to get pregnant and you’re still a bit concerned, just simply take a break from your intermittent fasts a few days before you ovulate.