A Complete Guide to Intermittent Fasting for Women

11 min read

This article was medically fact-checked by Consultant Obstetrician and Gynaecologist Dr. Shree Datta.

Please note that advice offered by Intimina may not be relevant to your individual case. If your period is late, you notice a strange change in blood color or you lose your period due to fasting, always consult your physician or other licensed medical practitioners.

Intermittent fasting is a really big thing right now.

Like really, big. 

There’s a lot of articles out there that talk about the best way to fast. The benefits of fasting. Workouts you can do while fasting. All kinds of different stuff.

The least talked about?

How it affects different genders. Specifically females.  There are many women who swear by it.

But there are also a few downsides that affect women specifically.

What Is Intermittent Fasting?

Intermittent fasting is basically not eating for a set number of hours and then eating whatever you want for the next set. Of course, there are certain foods better for you than others. And if you are looking for weight loss you may want to keep that in mind before you reach for that bag of chips. 

Since you aren’t eating for so many hours, it cuts down on calorie intake. Which generally equals weight loss. 

Some of the most popular methods are : 

  • The 16/8 method: Also called the Leangains protocol, it involves skipping breakfast and restricting your daily eating period to 8 hours, such as 12–8 p.m. Then you fast for the 16 hours outside that window.
  • Eat-Stop-Eat: This involves fasting for 24 hours, once or twice a week. One example of this would be not eating after dinner on a Tuesday until dinner time on Wednesday.
  • The 5:2 diet: With this method, you consume only 500–600 calories on two non-consecutive days of the week, but eat normally the other 5 days.
  • Alternate-day fasting: This routine is exactly as it sounds. You eat normally one day and then don’t eat at all (or only have a couple of hundred calories) the next. There’s a lot of different versions of this one. Make sure to find the one that works for you. 
  • The Warrior Diet: For this one, you eat small amounts of fruits and vegetables for most of the day and then have a big meal at night.
  • Spontaneous meal skipping: This one is pretty self-explanatory. You randomly skip a meal. You don’t have to follow a structured guide to reap the benefits of IF.

Who Is Intermittent Fasting For?

IF is most commonly used as a weight-loss tool. 

But that doesn’t mean it doesn’t have other health benefits. 

People who do regular intermittent fasting have shown improved markers of health, reduced risk of chronic health conditions, and improved brain health (1). 

Have you ever skipped breakfast? Chances are if you consistently do this, then you may have been intermittent fasting and not even known it!

Keep in mind, that research around IF is still somewhat limited, so people should proceed with caution – and discuss with their healthcare providers before starting a regime.

How Does IF Affect The Body?

Overall intermittent fasting has the same effects on the human body in the following ways(2):

1. Changes The Function Of Cells, Genes, And Hormones. 

It’s no surprise that not eating for a while can cause a change in your body. 

Here are a few things that happen when you fast:

  • Insulin levels drop: Dropped insulin levels are the reason that you lose weight. Because when your insulin drops you start burning fat.
  • Human growth hormone increases: This is the hormone that facilitates fat burning and muscle gain along with numerous other benefits.
  • Cellular repair:  The body starts cleaning out waste material from cells.
  • Gene expression: IF causes changes in several genes that have been known to relate to longevity and protection against disease.

2. Lose Weight

It is fairly well known that it will help you lose weight. 

But how does it do this? 

As mentioned in the last point — insulin levels drop and human growth hormone increases. These combined functions cause the body to start burning fat.

It also increases your metabolic rate — which means you burn more calories in the same amount of time. 

3. Reduce Oxidative Stress

Oxidative stress is one step towards aging and many chronic diseases.

Some studies have shown that intermittent fasting may help the body fight off oxidative stress.

4. Heart Health

There are a number of risk factors that IF may help to improve. These include blood pressure, total and LDL cholesterol, blood triglycerides, inflammatory markers, and blood sugar levels (3).

5. Brain Health

Several studies on rats have revealed that intermittent fasting may increase the growth of nerve cells. Which benefits brain function (4).

A Brain-Derived Neurotrophic Factor (BDNF) has increased levels while fasting. (5, 6). Low levels of BDNF have been linked to depression and many other brain problems.

It’s also said that fasting brings mental clarity, letting you focus better, and improving your memory.

Now, on to the big question.

Does Intermittent Fasting Affect Women Differently?

The short answer?

Yes. 

The long answer?

There’s a lot of differences between fasting for men and women because of our genetic makeup. Hormones in women react differently to a lack of energy supply compared to men. 

Below are a few ways that IF can affect women:

  • Can affect blood sugar control (7)
  • Alters reproductive (8
  • Thin and weak 
  • Missed periods
  • Heightened stress response 
  • Increased their spontaneous activity 
  • Improved their learning and memory 
  • Maintained elevated levels of circulating brain-derived neurotrophic factor (4)
  • Hormones

Because our hormones are so intertwined, throwing one-off can throw off something else. This imbalance leads to the list above.

One of the most concerning ways IF can affect women would be missing cycles or menstruation stopping altogether. 

Why Missing Your Period Is A Big Deal

You may think that missing your period because of intermittent fasting doesn’t really matter.  

It may have even happened to you once or twice before now.

But our periods are a really big indicator of how our body is doing. 

Your period’s not only a sign of fertility – it is also a sign of your overall health. 

Even if you aren’t trying to get pregnant, having your period is important and can clue you in to what is going on with your body. 

There are a few things that can cause you to miss your period:

  • Weight changes: Chances are that you are losing weight with your IF. That’s a good thing of course, but also has an effect on your period. It should resolve itself over time and get you back on a normal schedule
  • Stress: Not eating or getting enough of the nutrients you need can cause stress on your body, which causes you to miss your period. 
  • Too much exercise
  • Thyroid problems 

There isn’t a lot of research out there for intermittent fasting on humans. But we can compare a few of its effects with other research like ones on metabolic and lifestyle traits and behaviours such as weight, exercise, and caloric restriction.

Caloric restriction is a stressor in the brain’s world. This can modify the release of sex hormones through what is called hypothalamic-pituitary-gonada (HPG) axis. Hormones on the HPG axis regulate reproduction and fertility. 

It can also affect the balance of estrogen. Estrogen is the hormone that plays a big hand in female development. I’m taking the reproductive system along with our female characteristics like breasts.

Basically, if a woman’s body does not have the nutritional or metabolic energy that it needs to support a pregnancy, it just goes ahead and shuts off the reproductive cycle. 

This is why you may want to hold off on fasting if you are trying to get pregnant. At the very least, reach out to your doctor and discuss your options.

Can You Do Intermittent Fasting Without Affecting Your Period?

It’s hard to say how exactly it will affect your body and cycle. So there’s no set amount of fasting that says “stay under this #” and you’ll be fine.

A few days of fasting is unlikely to affect your period.

But it really comes down to diet quality, caloric intake, and BMI.

You need to keep an eye on what you eat and make sure that you aren’t having any nutrient deficiencies or low blood sugar levels.

And if you aren’t already, it’s a good idea to track your period. 

Not only does keeping track of your period let you know the length of your cycle better (no more surprises about your period coming) — it also helps you know what is normal for you. Some women’s periods are on a very tight schedule while others can vary from month to month.

It’s important to know what is normal for you before getting started.

If you know your normal cycle, you can more easily recognize what may have changed it.

And if your period does stop, reach out to your doctor to figure out what’s going on. You can also try switching to an easier exercise plan and eat foods with a healthy fat like avocados, coconuts, and almonds.

If you aren’t getting enough to eat it’s possible that you may develop amenorrhea. This is when you miss a period for at least three cycles. Generally, the most common cause of amenorrhea is pregnancy, which is a natural reaction from your body. It shuts down your period because it’s already pregnant. But low body weight, excessive exercise, and stress are also known factors. 

IF can cause hormonal imbalances as well. 

Hormonal changes can cause issues such as:

  • Polycystic Ovary Syndrome (PCOS): Your hormone levels run high instead of going up and down like they should with a normal menstrual cycle. These changes are not due to IF.
  • Thyroid malfunction: If the thyroid gland is over or underactive, it can cause irregularities in your menstrual cycle. Again, these changes are most likely not due to IF.
  • Pituitary tumor: A tumor in your pituitary gland can interfere with the regulation of hormones needed to regulate your menstruation.
  • Premature menopause: Generally happens around 50. But sometimes if the ovarian supply of eggs diminishes before age 40 and menstruation stops. 

A specific example of this is hypothalamic amenorrhea. 

This is when menstruation stops for several months due to problems with the hypothalamus — the hypothalamus is in the center of the brain and controls reproduction. This happens when there’s an energy imbalance, food restriction, weight loss, exercise, stress and genetics.

Now that you’ve got some awareness of fasting’s effect on your body let’s talk about some ways that you can do fasting.

You just need to take a more cautious approach.

Most Effective Fasting Approaches For Women

A lot of intermittent fasting studies have been done on rats, meaning there aren’t a lot of human studies to begin with. Even less for Women specifically.

This means there are a lot of opinions out there about fasting and it leaves us in a bit of a gray area. 

But some general guidelines are:

  • Don’t fast for longer than 24 hours
  • The ideal fasting window is 12 to 16 hours
  • Ease into fasting when starting out
  • Make sure to drink plenty of fluids while fasting
  • Keep exercise light on fasting days

Easing into fasting means don’t do consecutive days when you’re starting out. Start small with 3 days a week (every other day) for two weeks to start.

IF may be most effective for motivated individuals who are able to avoid overeating after a fasting period. Social butterflies beware – it can be difficult to follow a strict IF protocol when you’re out and about socializing. 

Intermittent fasting is only effective when you eat healthily during your meal periods. While there’s nothing wrong with the occasional indulgence, binging during your eating window will negate any positive effects of fasting.  

When To Avoid Intermittent Fasting

As you’ve read so far, IF can be a great tool — but it isn’t for everyone.

A few reasons to avoid intermittent fasting:

  • Pregnant or trying to get pregnant
  • Breastfeeding
  • Difficulty sleeping
  • Chronic stress
  • Previous history of eating disorders

IF is meant to complement a healthy lifestyle. So if you think you can eat junk food during your windows, you will most likely not reap the same benefits.

Should You Intermittent Fasting?

As with any kind of diet and exercise, there are risks associated with it. Make sure you take precautions.

And the most important thing you can do when trying out fasting is to listen to your body. There is nothing wrong with trying out a few different methods or tweaking them to find out which one works best for you.

If you have any questions or concerns, reach out to your doctor and discuss if it’s the right plan for you.

Facts Checked By:

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20 thoughts on “A Complete Guide to Intermittent Fasting for Women

  • Hello..This is my first month of fasting I’m doing omad(one meal a day) after my periods we’re over I’m experiencing a brown discharge from my vagina for whole of this week.this has never happened for this long. Before OMAD I would experience like 3_4days and it was over.but now it’s like a week and it’s not going away..Is it because I changed my diet ? Coz I don’t do carbs anymore just green vegetable s and proteins .. Kindly I would like to know.. Thank you.

      • Hi! Great article btw! I’m just concerned why I missed my period for 3 mos now (going 4th after Nov). Is it normal while doing 20:4/OMAD? I’ve been fasting for over a year now, but this is the first time that I’ve experienced this.

        • Hi Yannie! I would recommend that you talk to your GP or gynecologist if you’ve missed that many consecutive periods. There are a range of reasons why this can happen, from too-low body weight to perimenopause. When in doubt, see your doctor!

      • Hello!
        I also am experiencing dark brown blood discharge (light, but constant) after having fasted 16:8 for one week. I am midway through my cycle, so this is not part of my normal period. Is this normal? Should I stop fasting?

        • Hi Olivia, you should reach out to your doctor to figure out what’s going on. Every body is different and there is no one answer for all.

          • Hi, ive been doing 2 meals a day along with fasting for just one week and im experiencing the same
            Thing, this isnt normal for me either, did yours go away?

  • hi yes i just finished my period and started IF 16/8 and my period restarted again will it adjust and go back to regular

  • I’ve been fasting for a few weeks now. I usually fast for 20-21 hours. My period came a week early. Could this be because of the fasting?

    • Hi Tessa, maybe you can try with a shorter fasting window, but first of all, you should reach out to your doctor to figure out what’s going on because every body is unique.

  • I have been on diet for 3 weeks and intermittent fasting for 10 days. My period is almost 7 days of delay. Should i stop the IF?

    • Hi Eve, maybe you can try with a shorter fasting window, but first of all, you should reach out to your doctor to figure out what’s going on. Every body is different and there is no one answer for all.

  • Honestly I don’t feel like 12 or 13 hours should be considered “fasting” at all. (particularly in reference to “dangers for women”) It’s really just a reflection of our modern society’s food issues and nothing more. even the 16/8 would have been a totally normal situation for our hunter/gatherer ancestors… but in the 1950’s… like a generation or two ago… it was NORMAL for ALL people all the time, male and female to have 12-13 hours of non-eating a day. The kitchen closed after dinner and didn’t open again until breakfast the next day metaphorically speaking. So technically obviously it’s a fast because that’s why we even have the term “breakfast”, but I think it’s a problem that we live in a society now in which even 12 hours of non eating is considered some “wacky diet trend” with the idea that some people should be “concerned” about doing this on consecutive days.

    Honestly if all of society returned to a normal 12-13 hours without food each 24 hour window, we would see most chronic health issues nearly disappear. It’s the fact that people feel like they have to have a snack right before they sleep, so many people are only sleeping 6 hours a night, and then people feel like they have to eat the moment their feet hit the floor in the morning that’s the problem IMO. The digestive system needs a REAL break so other body systems can repair themselves. Most people are living in a state where their bodies are not completing all the repair they need because they feel like they can’t go 12-13 hours without eating.

  • Your article is great, easy reading and really informative. Can this be sustainable, more or less can it be a full lifestyle change. I feel great, I’ve been doing it now for 5 months, missed my period twice but my mental clarity is great. I’ve had problems sleeping before but those seem to have resolved themselves since i started IF as well.

    • Hi Mary,

      every body is different, you must advise your doctor before going on any kind of diet. Same as for the Intermitted fasting.

      Have a great day,

    • Hi Megha, 16:8 method is the easiest fasting method and perfect for beginners. You can start and pay additional attention to your body. If anything changes you can always stop fasting. Also, we suggest contacting your medical expert to be sure, especially if you had any medical problems in past.

  • heyy i’m 15 and I lost my period due (i think) to fasting. Are there ways to get it back?
    i have tried probiotics and green juice but nothing has worked and it has been over a year.
    thank you

    • Hi Ruth! If your period has been absent then we strongly recommend talking to your doctor, as tt may be indicative of a more serious health concern. Be open and specific about everything you have been doing before and after your period stopped coming, as there could be various causes including undereating or anemia.

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