Intermittent Fasting and Fertility in Women

Posted on Posted in Just For Women

How does intermittent fasting affect fertility in women?

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.




8 thoughts on “Intermittent Fasting and Fertility in Women

  1. Hi there,

    Thank you for your article. I really enjoyed it? Will fasting help me to lose weight due to estrogen dominance? I was going to give fasting a go to lose weight, but then read that fasting actually increases estrogen.. Is that right?

    1. Hi Jess, This depends on whats going on with your body right now. Every one is different. The state of your nervous system while fasting plays a big role. If you’re stressed out and you’re also forcing yourself to fast to lose weight quickly then yes you could be increasing the stress hormones cortisol and adrenalin in your body which can cause or perpetuate estrogen dominance. But if you’re fasting properly, intermittently, not for too long, in a relaxed state, and are enjoying the fasts then your body will be more able to use that time to detox. This will include detoxing the extra estrogen from your body. I highly recommend talking a green powder and liver support supplements to help your body do this and to minimise any stress it might go through if it has a lot to detox! I recommend something like these They will help with the detox process. I hope that helps.

  2. Hi,

    I am going to start ifasting in next week, I am on TTC for 1 year and no luck yet. I thought to ifasting to lose 9 pounds to get in to my healthy weight. Will it affect to the reproductive system?

    1. Hi Shani,

      There are many factors that can affect your fertility including stress, diet, too much exercise, if you’re deficient in nutrients etc. Intermittent fasting, when done properly, is a natural way of eating so should not affect your ability to get pregnant at all. The main thing is to ensure you’re eating healthy and getting all of your needed nutrients and calories on the days that you don’t fast. Also by keeping stress to a minimum because long term stress can throw off our hormones! All the best.

  3. Hi there,

    I have been on the 5:2 diet (having upped the number of fast days to 3) for 12 weeks now. I have lost around 8 kilos and since about week 2 have not had my period. Could you advise whether you believe this May be a sign of me doing damage to my fertility? I am concerned after reading an article about this which stated 30% of young women within a healthy weight range (of which I am both) , had their periods disappear for good.

    Any info you could provide on my case would be much appreciated.

    Many thanks

    1. Hi Amy,
      That’s a great question. The loss of your period could be for a number of reasons and I would need to know a little bit more about your fasting schedule and general lifestyle etc. If you’re ifasting properly (intermittently, for up to 24 hours, and maintaining normal and healthy eating habits for the rest of the week) it shouldn’t affect your periods or fertility. However if you’re also cutting calories during the rest of the week and adding excessive exercise or even just have other ‘stressors’ going on in your life then yes, your body could be going into survival mode and the ‘flight and fight’ response may be kicking in. When that happens your periods and your ability to fall pregnant are moved to the bottom of your body’s priority list as it thinks you’re in a crisis situation and will just focus on surviving. If you are planning on getting pregnant then I would have a good look at everything else going on in your life and make sure you cut down on as many stressors as possible. They can be a stressful job, high alcohol consumption, too much caffeine, poor sleep, even emotional traumas. If you’re not enjoying your fasts or doing too many of them, then your body might react to them as ‘stressful’ as well. I highly recommend a book by Dr Libby called ‘Rushing Womans Syndrome’ which includes fertility and how us women can load up with stressors in our life which can affect our hormones and fertility. Even the process of losing weight can be stressful in itself! Did you start/change any thing else when you starting fasting 12 weeks ago? Here’ s the book anyway and a recent TED talk of hers that you might find interesting I also recommend seeing a Naturopath or holistic nutritionist (or your doctor if you’re not in to naturopaths!) to have a look at how your hormones and adrenals are functioning. I hope that helps.

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