Why Intermittent Fasting Is Not Good For Your Menstrual Cycle

Cycling women’s bodies are not men’s (or menopausal women’s) bodies.

Intermittent fasting has become a popular approach, and there’s many studies showing benefits. Unfortunately, there are a lot of ways it can negatively impact cycling women’s bodies.

Here’s what can happen:

👉Loss of menstrual cycle
👉Fertility issues
👉Over-reliance on coffee (which can negatively impact adrenal function)

The thing about a cycling woman’s body is that it needs to feel safe in order to grow and house another life.

Whether your goal is to carry another life or not, your hormones will react to major fluctuations around food intake. These fluctuations can signal “famine ahead – things are not safe.”

**For those interested in the sciency-stuff: Food and calorie restriction cause a stress response in the body. Gonadotropin-releasing hormone (GnRH) is released by the hypothalamus to signal to the pituitary to produce both Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH). These hormones tell the ovaries to produce estrogen and eventually, to ovulate.

The hypothalamus and pituitary are very sensitive to stress, including not being fed enough calories in a consistent pattern throughtout the day. Therefore will down-regulate both FSH and LH production, hindering ovulation.**

Many scientific studies still focus on men, or a combination of men & women. We don’t know how the numbers ultimately shake out.

Here’s the results of a few studies on reproductive females (humans & animals):

👉“An acute (48 h) total fast induced parasympathetic withdrawal with simultaneous sympathetic activation.” This study basically found that the women were kicked into their sympathetic nervous system during the fast. Our sympathetic nervous system triggers the release of adrenaline, which can eventually impact cortisol production.

The more your body focuses on cortisol production, the more it down-regulates your sex hormone production. This can lead to anovulatory cycles or hinder your progesterone production, leading to increased PMS, heavier menstrual bleeding, and more.

👉A study on young rats found that intermittent fasting negatively impacted the feedback loop between the brain and the gonads (i.e. ovaries), diminishing fertility.

👉 Another study found that while men had no change in glucose response and a significant reduction in insulin response after 3 weeks doing IF, glucose response was impaired in women.

👉 Not eating for several hours after waking can lead to cortisol spiking (especially if you drink coffee on your “fast”) and insulin increasing. One study found that although women following IF lost weight, their fasting insulin was increased. This is hard on your adrenals and will eventually down-regulate sex hormone production.

Now, I understand that there are some cycling women out there who have benefited greatly from IF. **Please note** we are individuals, and the way that are bodies react to things is dependent on a number of factors. Your stress levels, gut health, adherence to your circadian rhythm, and genetics all play a role in how your body responds to IF..

But if your:

Cycle goes whacky (even if it’s months after you’ve started practicing IF)

You are skipping periods, or you

Start to have hot flashes but aren’t close to menopause

I’d take a second look at what fasting might be doing to your body.

Remember, your period is your fifth vital sign. And our bodies want to feel safe, nourished, and taken care of in order to ovulate, and ovulate well.

Other Considerations

In general, women tend to have more of a history with disordered eating than men. IF can unfortunately play into old mindset and patterns without women always realizing it.

It also seems that fasting can impact our thyroid, which controls our metabolism. Intermittent fasting was shown in this study to lower T3, which is our active thyroid hormone. So many women struggle with their thyroid – particularly as we age – and the active T3 can be tough to dial in. It’s worth considering if IF is helping your metabolism or hindering it.

What Do I Recommend?

Generally doing a 12-hour fast (13 hours at the most). This amount of fasting is usually safe for most people. It’s pretty much how people ate for a long time until late-night pizza places were invented. Eat dinner at 7pm, then breakfast at 7 or 8am, and you are golden.

Of course there are some people that need blood-sugar balancing to the point that even 12 hours is too much time to go without food. But if you are generally healthy, a 12-hour fast can provide a lot of the benefits of IF without triggering a negative cascade for your hormones.

Want to learn how to calm your cortisol and make your hormones happy? Check out my course “Why Making Yourself Number #1 Is The Only Way Your Hormones Are Gonna Chill The F Out.” If you want to understand the basics of how your hormones work, take a peak at “What The Hell Are My Hormones Doing?

What's Your Hormone Issue? Take this 2-minute quiz to find out!


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