You may have heard of intermittent fasting being the key to weight loss or the best way to control your cravings from a podcast or your favourite influencer on social media. There is no denying, intermittent fasting can help you to lose weight and can be a tool to help those who are struggling with Type 2 Diabetes. However, its impact on female hormones, especially reproductive hormones, is a topic that is not well favoured in scientific research (spoiler alert!). In this article we explore intermittent fasting and it’s effect on female hormones, focusing on reproductive health, menstrual cycles, fertility and overall hormone balance.

What is Intermittent Fasting?

Intermittent fasting is an umbrella term which is used to describe an approach to eating where an individual is restricted to consuming food, or calories, within a specific time frame. There are currently three widely known intermittent fasting approaches:

Alternate Day Fasting

This is where you may have days of eating, and days of fasting. You can eat as much as you want on the days you can eat, but on fasting days you can only consume water or less than 25% of your energy needs.

 

The 5:2 Diet

A modified version of the above, where you feast for 5 days and fast for 2 days per week. 

 

Time Restricted Eating

This involves confining your eating to a specified window of time (typically lasting between 4 to 10 hours) and fasting around this, with the exception of zero-calorie beverages. 

 

As women’s health experts, it hurt even explaining these to you, but we will always tell you the truth. There is research that shows that the various forms of intermittent fasting are effective for decreasing body weight, improving insulin sensitivity and blood pressure in males or adults suffering with obesity. 

But here’s the thing, intermittent fasting has an effect on SO many aspects of the body and how we function, and all of them are interlinked. 

 

What we do know is that for females, intermittent fasting negatively impacts:

  • Fatigue
  • Stress levels
  • Delayed Onset of Muscle Soreness (DOMS) from exercise
  • Sleep quality

 

What about the impact on female hormones?

How intermittent fasting affects female hormones on their own, is not completely understood yet. Research is in its infancy when exploring the direct effect on female hormones, but we do understand the indirect influence.

Have you ever experienced your period being delayed, or missed completely when going through a stressful time? Perhaps you slept terribly for a period of time, and you didn’t ovulate that cycle? Or, your menopause symptoms were through the roof! This can be that indirect impact.

How exactly these fasting approaches impact each hormone is a little complicated and depends on multiple factors:

  • Your age
  • Your current health status
  • What type of fasting you are doing

 

The real problem with intermittent fasting and female hormones (particularly estrogen and progesterone that play crucial roles in regulating your menstrual cycle, pregnancy and other aspects of womens health), is that hormones are very sensitive to change. When it comes to intermittent fasting In particular, two things:

  1. Energy Intake – When intermittent fasting, your energy intake changes. We tend to find that when restricting the time you are ‘allowed’ to eat, most women tend to eat less than normal.

    Unless you have been living under a rock for the last 10 years, you’ll know that in general, we are fighting an epidemic of women who under eat without any kind of dietary intervention like intermittent fasting. So this is very bad news!

    If you’re under eating, or more importantly, underfueling your body as it is, implementing intermittent fasting exasperates this. Leaving your body with even less energy to use to regulate all the important functions (including your menstrual cycle) and producing a huge stress response.
  2. Meal timings – Just as much as we like routine, our bodies love routine even more! Our bodies have a great reason for this, too. We’re going to try and explain it in simple terms:


Throughout the day, our hormones (all of them, not just female hormones) are fluctuating up and down. They are all very specific and need to be at a certain level at each time point during the day.

When we wake up in the morning, our hormones are a little all over the place. To put this into some ‘easy to understand’ context, the same thing occurs in men.  This is why they wake up with an erect penis…it is a result of their hormones being heightened in the morning too! There are many things that help us to regulate our hormones in the morning, but a very important one for women in particular is by eating breakfast every day. This is because of the close link between insulin and estrogen.

This lack of energy from intermittent fasting, or irregular meal times may lead to what we call anovulatory cycles, where you are having a cycle but not ovulating, or irregular or missed periods, known as amenorrhea.

Either way, this is very bad news for your health!

Is intermittent fasting good for fertility?

In short, no. 

If you are thinking of trying intermittent fasting in a bid to improve your chances of getting pregnant or improving your fertility, you are going down the wrong path. 

Having your female hormones in check and functioning optimally is pivotal for your fertility. As I have already mentioned, your hormones are very sensitive to any changes that we make, especially ones that negatively impact them. By intermittent fasting, the orchestration of your estrogen, progesterone, lutenizing hormone and follicle-stimulating hormone are likely to be negatively influenced. Intermittent fasting, coupled with intense exercise is a big no-no.

We explained this earlier with the anovulatory cycles, or amenorrhea, which is a risk when intermittent fasting. We don’t recommend intermittent fasting if you are trying to get pregnant, or thinking of having a baby soon.

 

Is intermittent fasting good for pregnancy?

Intermittent fasting is not recommended for pregnancy, for numerous reasons:

  • Generally, it is not recommended to be restricting food at all during pregnancy. The NHS recommends 3, healthy and well-balanced meals each day. 
  • There is no reason to intermittent fast. If you are overweight or obese when pregnant, your focus should be looking at your current diet and how to improve it with portion size and food selection. 
  • There is no reliable scientific research that has examined the effects of intermittent fasting on pregnant women. Therefore, it is not recommended. 
  • Animal studies are inconclusive. Some studies showed that fetal development was negatively impacted, some studies reported that the animals showed positive signs from the animal mother intermittent fasting during pregnancy. 
  • Hormone balance is essential during pregnancy, to ensure the safety and progression of the pregnancy. It is impossible to know how your body will respond by intermittent fasting during pregnancy, so it is best left alone.

The only time intermittent fasting may be considered by a dietician, is with gestational diabetes. If you have been diagnosed with gestational diabetes during pregnancy, you should be referred to the dietetics team at your local hospital. They will assess your case individually, and recommend the best dietary approach to manging your gestational diabetes.

 

Is intermittent fasting good for the postnatal period?

This is a difficult one to answer, because it depends on the timing as well as the motivation behind your intermittent fasting. 

0-9 months postpartum

We do not recommend intermittent fasting during this time. Your body has gone through a HUGE event called childbirth (yes, this absolutely does include c-sections as well!) and your body needs as much nutrients and routine as possible. What we mean by that is: regular, healthy meals. This, along with some rest, are the only things that will help your body recover. 

9 months+ postpartum

At Blossom Wellness, we do not recommend intermittent fasting, period. However, we recognise that for some women this approach works for them when trying to lose weight or address cardiovascular issues such as high blood pressure or addressing obesity. 

It is at the 9+ months postpartum, that we recommend speaking to your GP or a dietician about whether intermittent fasting could be a suitable option for you, and how to do it.

 

Is intermittent fasting good for menopause?

No, no and no again. 

Menopause is categorised by a decline in estrogen, and alongside this is a constant dose of fluctuating hormones. By adding intermittent fasting into the mix, this only further complicates these hormonal processes, which is going to exacerbate your menopause symptoms. 

I don’t know about you, but that is a resounding no from us!

Here’s the caveat

There is evidence to show that women that are postmenopausal and suffering with cardiovascular diseases may benefit from intermittent fasting for a short period of time, to help address and improve the outcomes of the cardiovascular diseases such as:

  • Coronary Heart Disease
  • Stroke
  • Peripheral Arterial Disease
  • Aortic Disease
  • Hypertension
  • Type 2 Diabetes
    and more.

Before you go

Before you go, we want you to know that there are other ways to address any goals, or concerns that you may be having. 

From our experience, people tend to look into intermittent fasting typically for weight loss. If you have found yourself reading this article with weight loss in mind, we want you to know that there are healthier and more sustainable ways to lose weight. 

Intermittent fasting is a restrictive diet approach. Unless you are advised by a medical professional to follow this approach, we say stick to eating your three meals a day and especially do not skip out on your breakfast!

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