A few years ago, when I was studying Kinesiology in Melbourne, my teacher told the class that we should all try intermittent fasting. Like with most things people tell me, I followed his advice blindly. That was until my friend came in one day and shared with the women of the class that fasting may not be so good for our hormones. Turns out, she may be right. So, why does it work better for men than women? And how can it affect our hormones, really? Here’s the truth about intermittent fasting – for women.

Why you should eat when you wake up

Let’s start with breakfast – the most important meal of the day. For pre-menopausal women, ideally you want to eat within the first 60 minutes of waking. It’s also important for this meal to be nutrient-dense and balanced – enough protein, fibre, carbohydrates, and fats. The reason for this is – regulation of blood sugar and our hormones. When you go about your day without eating, your adrenals produce cortisol in order to release stored glucose and maintain your energy levels. Over time, if skipping breakfast becomes a regular habit, the body learns to run off stress hormones like cortisol and adrenaline. With these elevated, the hormones that are considered less important (your sex hormones & their functions) fall to the wayside.

The difference between men & women

As we all know, men and women produce different hormones. We also have different levels of a protein called kisspeptin. Kisspeptin is responsible for the release of gonadotropin-stimulating hormone (GnRH), which controls the release of sex hormones in both males and females. Interestingly, females actually have more kisspeptin than males, which could mean that they are more sensitive to changes in energy balance within the body. Women are therefore more susceptible to a drop in kisspeptin – a result of intermittent fasting. Although rather complex, the cycle looks like this: fasting causes changes in hormones leptin, ghrelin, and insulin (related to fullness, hunger, and blood sugar balance, respectively). The fluctuations of these hormones then cause kisspeptin to drop, which results in a dip in GnRH and the sex hormones that it controls.

The other notable difference between men and women – we need a body that’s fuelled and healthy enough to sustain a pregnancy.

Studies on intermittent fasting

A lot of studies you’ll find on the web regarding intermittent fasting will have a sample involving only men or women who are post-menopausal. This is because, typically, results are the most favourable for men and women who don’t menstruate (due to their differing hormonal profile). When doing research for this post, I did, surprisingly, find a 2022 study that included pre-menopausal women. The study found that hormones testosterone and androstenedione remained constant in both fasted men and women. But, DHEA – the hormone that affects egg quality and ovarian function – was 14% lower in women (both pre & post-menopausal) at the end of the 8 weeks. What’s most important to note is that the study did not test estradiol, estrone, and progesterone (the hormones vital to pregnancy) in pre-menopausal women.

So, while intermittent fasting does have some benefits, these benefits do not typically lend themselves to women who ovulate and menstruate. We need nutrients and calories, and we need them often. And as someone whose life revolves around breakfast, I can’t say I’m mad about it.

Yours,

Kait x

Cover photo by Kool Shooters