Nutrition

Intermittent Fasting for Women: Everything You Need to Know

Teresa Pires de Lima

Nov 21, 2023 • 9 min read

Intermittent fasting has become a trendy dietary approach in the last few years, and that's no surprise - who isn't attracted to a "diet" where instead of food restrictions you only have to worry about time restrictions?

Weight loss, reduced inflammation, better management of diabetes, and enhanced cellular repair mechanisms are just some of the many promising benefits intermittent fasting has to offer - sound about perfect, right?

However, intermittent fasting is not as perfect as it seems. Like a lot of things, most of the related research is done on men - and we all know that our bodies are extremely different.

In this article, we aim to provide you with a comprehensive understanding of Intermittent Fasting, the research behind it and how you can approach it, if it's suitable for you, in a safe and healthy manner - that supports your female hormones.

First let’s cover the basics:

What is Intermittent Fasting?

Intermittent fasting is not a diet in the conventional sense but rather an eating pattern that cycles between periods of fasting and eating. It emphasises when you eat rather than what you eat.

What are the different types of fasting?

The 16-8 fasting method, also known as the Leangains protocol, involves fasting for 16 hours and restricting your eating to an 8-hour window.
Alternate-day fasting involves alternating between days of regular eating and days of fasting or consuming very few calories.
The 5:2 diet involves consuming a regular diet for five days a week and drastically reducing calorie intake (usually around 500-600 calories) on two non-consecutive days.
The eat-stop-eat method involves fasting for a full 24 hours once or twice a week.

What does intermittent fasting do to a woman’s body?

The impact of fasting on hormones and the menstrual cycle can vary greatly among individuals. Some women may tolerate intermittent fasting well and experience positive effects, while others may encounter changes in their menstrual cycle - there are many anecdotal stories of women experiencing disruptions to their menstrual cycles.

One alarming study done on rats by Kumar et al. presented menstrual irregularities and fertility issues that started a whole snowball effect on the safety of intermittent fasting in women of reproductive age. However, this study was done on 3 month old rats (which would translate into 9 year old humans) - kinda sketchy right? Still, these findings are concerning and demand further investigation! But Rome wasn’t built in a day and high-quality studies on humans take a lot of time… So let's look at the studies we have at the moment and try to find reasonable conclusions from those, shall we?

Health Benefits of Intermittent Fasting for Women:

Intermittent fasting is associated with health benefits like lowering blood pressure, improving mental health, improved insulin sensitivity, weight loss, and reduced inflammation.

Improved Insulin Sensitivity: intermittent fasting may enhance insulin sensitivity, which can be particularly beneficial for women with insulin resistance or polycystic ovary syndrome (PCOS). Improved insulin sensitivity can help regulate hormone levels and menstrual cycles.
Weight Management: Maintaining a healthy weight through intermittent fasting may support hormonal balance. Excess body fat can lead to hormonal imbalances, and weight loss achieved through intermittent fasting may help mitigate these issues.
Reduced Inflammation: Lowering inflammation through intermittent fasting may benefit women with conditions such as endometriosis or autoimmune disorders, as these conditions are often associated with chronic inflammation.

Is Intermittent Fasting Bad for Women's Hormones?

The relationship between intermittent fasting and female hormones is complex and can be both good and bad, it’s all about how you do it! Here are some things to take into account, remember we’re all different and the research is still a little bit shaky!

Gonadotropin-releasing hormone: our bodies are notably sensitive to caloric restriction. When women engage in prolonged or excessively frequent fasting, it can lead to a reduced calorie intake, impacting a critical part of the brain known as the hypothalamus. This impact can cause a disruption in the release of gonadotropin-releasing hormone (GnRH), which plays a pivotal role in regulating the release of reproductive hormones, specifically luteinizing hormone (LH) and follicle-stimulating hormone (FSH). The disruption in GnRH secretion can lead to a breakdown in communication between these hormones and the ovaries. This miscommunication can result in a range of health issues, including irregular menstrual cycles, infertility, compromised bone health, and other related health consequences.
Estrogen: as mentioned earlier, intermittent fasting can improve insulin sensitivity. Improved insulin sensitivity can lead to more stable estrogen levels, reducing the risk of conditions associated with estrogen imbalances, such as menstrual irregularities, certain reproductive issues, and mood fluctuations.
Progesterone: when we fast for long periods, our cortisol (AKA stress hormone) goes up, which will make progesterone go down. Hormonal imbalances in the luteal phase can result in shorter luteal phases, making it difficult for women to conceive. To keep your progesterone levels up its important to fuel your body.
Thyroid Hormones: The thyroid gland plays a crucial role in regulating metabolism, and thyroid hormones, including triiodothyronine (T3), are integral to this process. Some studies have suggested that intermittent fasting may decrease T3 levels, potentially slowing down the metabolism. In the long run, lower T3 levels may lead to symptoms like fatigue, cold intolerance, and hair loss.

It's important to approach intermittent fasting cautiously and tailor it to your specific needs and sensitivities. Monitoring your body's response, seeking guidance from a healthcare professional, and making adjustments as necessary are key steps to ensure that fasting aligns with your hormonal and menstrual health.

Intermittent Fasting protocols for women

Well, first of all, by tracking your cycle! It's very important for women to be aware of our menstrual cycle phase when fasting because we want to keep our hormones well and balanced. Then it's important to start slowly, you want to build up your fast - start at 12 hours and gradually build up from there. Here is a guide on how to fast throughout the lifecycle:

For women under 40:

Note: this is an example for a 28 day cycle - your cycle can be anywhere between 21 to 35 days.

Early Follicular Phase (Day 1-5): This is your period time, and guess what? Both progesterone and estrogen are hitting a low. The best game plan? Start thinking about fasting around day 3 of your period.
Late Follicular Phase (Day 6-14): Now we're talking! Your estrogen is on a climb to the top. This is your moment to amp up the fasting game. Longer fasts? Absolutely – if you're feeling bold and ready, now’s your golden window!
Ovulation and Luteal Phase (Day 15-28): Alright, time to hit the brakes on fasting. Progesterone is stepping up its game, and we don’t want to throw it off.

For women over 40:

Again, track your cycle! This is a time when your cycle can undergo significant changes so it's important to keep a close eye on it.
Follow the same tips as above, but remember to personalise this carefully to yourself.
When you reach day 21 start fuelling up on some hormone building foods like beans, squashes, potatoes, rice, grass-fed beef, citrus fruits, and tropical fruits - we want to keep that progesterone up!

For post-menopausal women:

Now’s the time to fast whenever you feel up to it!
During your eating window, prioritize nutrient-dense foods.
Give yourself a break once a week - instead of fasting, feast!

Who should not be doing Intermittent Fasting?

Women dealing or with a history of eating disorders;
Women and people who are pregnant;
Women and people who are breastfeeding;
Women with thyroid conditions should consult a professional;
Women who are taking certain medications should consult their doctors.

How to break your fast?

That first meal after a fast should be carefully chosen - you want to include high-fiber, high-protein foods and mix it up with healthy fat sources in order to avoid a big blood sugar spike. Including all those gut-loving pre- and probiotic foods will also add to your meal. Here are some examples of foods to include:

High fiber:

Lentils
Chia seeds

High protein:

Eggs
Greek yogurt

Healthy fats:

Avocado
Nuts

High Prebiotic:

Garlic
Flaxseeds

High Probiotic:

Kefir
Kimchi

Why I am not losing weight with intermittent fasting?

While intermittent fasting is a great tool for weight loss, it might not do the job alone! Several factors can influence weight loss during intermittent fasting:

Calorie Intake: Even with intermittent fasting, consuming excessive calories during eating windows can hinder weight loss. Ensure you maintain a calorie deficit for weight loss.
Nutrient Quality: The quality of the food you eat matters. Focus on nutrient-dense, whole foods to support your health and weight loss goals.
Hormonal Factors: Hormonal changes in women can affect weight loss. Stress, sleep, and hormonal imbalances can impact results. Consult a healthcare provider if necessary.
Exercise: Incorporating regular physical activity is crucial for weight management. Combining exercise with intermittent fasting can enhance results.
Patience: Weight loss may not always be rapid. Be patient and consistent with your fasting routine, and remember that individual responses vary.
Metabolism: Metabolism can slow down with age. Consider consulting a registered dietitian or nutritionist for personalized guidance.

Take home:

Intermittent fasting is definitely a neat trick for shedding some pounds and boosting your overall health. But hey, it's important to remember that men and women might have different experiences with it, and there isn't a ton of research out there on the effects on female bodies. So, if you're thinking about giving intermittent fasting a try, it's probably smart to have a chat with your doctor first. They can help you figure out if it's a good match for you and clue you in on any risks you might not have thought about. Also, don't underestimate the power of tuning into your body's cues. Paying attention to your cycle and how you're feeling can really be eye-opening – sometimes your body knows what's up before you do! So, go ahead and give it a try, but stay safe and listen to what your body's telling you. Happy fasting!

References

Functional hypothalamic amenorrhea and its influence on women's health - https://pubmed.ncbi.nlm.nih.gov/25201001/

Role of therapeutic fasting in women’s health: An overview - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4960941/

Effects of Intermittent Fasting on Hypothalamus–Pituitary–Thyroid Axis, Palatable Food Intake, and Body Weight in Stressed Rats - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10005667/

Effects of Intermittent Fasting on Hypothalamus–Pituitary–Thyroid Axis, Palatable Food Intake, and Body Weight in Stressed Rats - https://www.cell.com/cell-metabolism/fulltext/S1550-4131(19)30429-2?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS1550413119304292%3Fshowall%3Dtrue

Estrogen: an emerging regulator of insulin action and mitochondrial function - https://pubmed.ncbi.nlm.nih.gov/25883987/

How Intermittent Fasting Affects Women - https://health.clevelandclinic.org/intermittent-fasting-for-women/#:~:text=“Fasting

Effect of Intermittent Fasting on Reproductive Hormone Levels in Females and Males: A Review of Human Trials - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9182756/

Intermittent fasting dietary restriction regimen negatively influences reproduction in young rats: a study of hypothalamo-hypophysial-gonadal axis - https://pubmed.ncbi.nlm.nih.gov/23382817/

Effects of Intermittent Fasting on Health, Aging, and Disease -https://www.nejm.org/doi/full/10.1056/NEJMra1905136

Effect of a Six-Week Intermittent Fasting Intervention Program on the Composition of the Human Body in Women over 60 Years of Age -https://www.mdpi.com/1660-4601/17/11/4138/htm