Should You Fast During Your Period: How Fasting Affects Your Cycle

I often talk about easing off on intermittent fasting and/or keto during the seeking leading up to your cycle, but the idea for this post came up from a recent experience trying to implement my 5-day keto vegan meal plan (I will tell you all about it). We will talk about everything that relates to fasting at different stages of your menstrual cycle, including should you fast on your period, when should you start fasting after your period, and menstrual irregularities due to fasting.

How We Define Fasting

Before we get into all the details about fasting during your menstrual cycle and answer the question should you fast on your period, let me make sure we are all clear about why I mean by fasting. Most often than not, when we refer to fasting, we mean a water fast (no calories at all). However, the info in this post applies to modified fasting and intermittent fasting a well.

What Is a Modified Fast

I use the term modified fast to talk about the Fasting Mimicking Diet (a severe calorie restriction with a specific macronutrient ratio). We could extend the definition to any type of food deprivation like protein or carb restriction, for example. Whenever you change your diet, it stresses your body. The change in itself might be positive and the stress on your body desirable (exercise is a stress, we need a certain amount of stress), but depending on what you are changing, it may affect your menstrual cycle.

Intermittent Fating and Your Menstrual Cycle

Intermittent fasting without any type of food restriction may or may not affect your cycle. It most likely will depend on how much practice you have had with intermittent fasting, how long you fast each day and how many days a week. If you are wondering about intermittent fasting, just read the information below and see whether it applies to you. It’s up to you to experiment and see what works for your own body.

Shoud You Fast On Your Period

The first question I want to address is should you fast on your period. The simple answer is yes, but there are some caveats as usual. You may find that some months are different than others. Getting back to my keto vegan experiment, I ignored my own advice and attempted to follow my keto vegan meal plan during the week leading up to my period. It was impossible. I felt way more hungry than usual and had way more cravings too! I tried four days in a row and gave up every single day. Then, on day 1 of my cycle, it’s like everything went away! The cravings, the insatiable hunger, the inability to stick to the plan. Most months, for most of you, facing on your period is fine (day number one of your period is day number one of your cycle). You will be able to pick up everything where you left off during the week leading up to your period.

Why You Shouldn’t Fast the Week Before Your Period

Before we even get into the biological reasons why it’s best to avoid fasting the week before your period, let’s just learn to listen to your body. Take a few months to observe what happens and how you feel throughout your cycle. You will most likely notice that your hunger and your cravings for carbs increase during the last week of your cycle. That’s because your body needs carbs to regulate your sex hormones.

Carbs, Fatty Acids and Your Sex Hormones

Yes, your sex hormones are fat-soluble molecules made from cholesterol. That’s why always including plenty of healthy fats in your diet is important to maintain your cycle regularity as well. I love using plenty of extra virgin olive oil, avocado, nuts, and seeds in my meals and salads. Restricting carbs tends to decrease your leptin levels by decreasing the production of insulin, which tends to be a good thing, but it can also alter your hormonal function. Leptin receptors have even been found on your ovaries! It is involved in the HPA axis, which controls your hormones.

The Meditteranean Diet is an excellent starting point to learn how to use an abundance of healthy fats without restricting carbs. Check out my Mediterranean Diet Book for further guidance.

HPA Axis

A quick word about the HPA Axis. HPA Axis stands for hypothalamic-pituitary-adrenal axis. The main function attributed the HPA Axis is your body’s response to stress. As you may know, your sex hormones are sensitive to chronic stress, which brings us back to how any stress whether physical or psychological may affect your menstrual cycle.

Photo Credit: Hungry Hobby

Fasting and Your Menstrual Cycle

Now, you have the answer to the question should you fast on your period and understand how fasting may cause a cascade of hormonal reactions that affect your period. Let’s talk about some specific issues that sometimes arise.

Missed Period Due to Fasting

As a reminder, the week before your period is when you are most susceptible to the stress of fasting because your level of estrogen drops at that time. Take it easy during the last week of your cycle to avoid menstrual disruptions. It is possible to miss a period due to fasting. I would venture to say it is rare since of all the questions I get about fasting, this one hasn’t come up. If it does happen to you, take time off from fasting until the issue is resolved. Once it is resolved, start with intermittent fasting only 12 hours a day and move up from there.

Spotting During Fasting

Spotting during your cycle isn’t normal. Again, it could be a sign that you are putting too much stress on your body. Take a step back if you notice spotting during fasting. There are many possible causes that you may consider looking into and I suggest you read the article Spotting Between Periods. It is very helpful and informative.

Ramadan Fasting’s Effects on Menstrual Cycle

We are going to briefly talk about how to practice intermittent fasting safely during your cycle, but before we do, I wanted to point out an interesting study that was done about Ramadan Fasting’s Effects on Menstrual Cycle. During the month of Ramadan, Muslims abstain from food and drink from dawn to sunset (this could mean anywhere from 10 to 21 hours depending on where you live). The study confirmed many menstrual abnormalities, particularly for women who participated for longer than 15 days. These abnormalities included:

  • Oligomenorreah: Infrequent periods (fewer than 6 to 8 periods a year)
  • Polymenorrhea: A cycle that is shorter than 21 days
  • Hypermenorrhea: Abnormally profuse or prolonged menstrual flow

Again this confirms how the stress of fasting can affect your menstrual cycle.

Intermittent Fasting and Your Menstruation

The advantage of intermittent fasting is that it is easily customizable to suit your needs. You don”t need to fast every day, you don’t need to fast long. That’s where learning to listen to your body is essential. Some women may prefer fasting only 12 hours every day while some women may benefit from a 24 hour fast only once a week. It’s up to you to find the method that works for you. If you are still trying to decide which method to use, you may enjoy reading How to Decide Which Intermittent Fasting Method Is Best for You.

Does Intermittent Fasting Help With Period Cramps

We talked about all the ways fasting can stress your body and affect your menstrual cycles, but did you know that some women find relief from period cramps when they practice intermittent fasting? Yes, fasting can be a stress. On the other hand, reducing your insulin level may also create a cascade of benefits that will affect your cycles in a more positive way. I noticed it myself. My cycles have become more regular and less abundant since I started intermittent fasting 2 years ago. I enjoy more energy than ever, I feel amazing, my mood is stable and my cycles are regular. However, it is important to emphasize that I have learned to listen to my body. I never deprive myself during the week before my period. Instead, I make sure I eat when I am hungry and I indulge in more carbs during that time as well.

Fasting and Your Menstrual Cycle Video