Intermittent Fasting and Period

Intermittent Fasting and Period

The female body is known to have hormonal fluctuations throughout the month, which can sometimes create a challenge for women to follow a fasting protocol, especially during their period.

But does it mean that fasting during menstruation isn’t possible? Of course not! In this guide you’ll find the hacks that every woman should know if they want to integrate intermittent fasting into their daily life without disturbing their hormonal balance.

Intermittent fasting is known to have many health benefits, including weight loss, balanced blood sugar level, lower blood pressure, improved mental clarity, increased energy, glowing skin, etc.

Most men can adopt this nutrition system very quickly and start experiencing these health benefits in a couple of weeks. Whereas the same may not be the case for all women who started doing intermittent fasting, as some report having brain fog, cravings, and sometimes even weight gain!

If you’re a menstruating woman, rest assured that intermittent fasting during menstruation is totally OK if you simply implement some minor changes during the month. Just get to know your menstrual cycle’s anatomy so you can adjust your fasting routine according to your own menstrual cycle.

How can I continue fasting during periods?

For a woman, maximizing the benefits and reducing the side effects of intermittent fasting depends on syncing her fasts to her menstrual cycles. To set a routine, you must first understand how the hormonal cycle works.

A woman’s hormones fluctuate in a four-week cycle during her child bearing years. This cycle consists of three main phases:

  1. Follicular (Day 1-10 of the cycle)
  2. Ovulation (Day 11-15 of the cycle)
  3. Luteal (Day 16-28 of the cycle)
  • The menstrual cycle starts on the first day of a period. 
  • Bear in mind that every woman’s menstrual cycle is unique. The length of each cycle and its phases can vary based on your age and genetic factors.


The follicular phase starts on the first day of your period and lasts around 14 days. During this period your estrogen level increases day by day to help prepare the uterus for a potential pregnancy. This 2-week phase is perfect for longer fasts (like 16/8 or 18/6 plans), as you’ll be more energetic. 

  • Important note: The 18/6 intermittent fasting plan or other plans like the warrior diet (20/4 plan) with longer hours of fasting may not be suitable for all women. If you want to follow one of these, try the plan for a few weeks and listen to your body’s signals very closely, as you may suffer period cravings or other side effects.


Around days 11-15 of your cycle, ovulation occurs. You can replace your existing fasting plan with a shorter fasting window like the 12/12 or 14/10 fasting plan during ovulation.

If there’s no pregnancy, the hormones shift into the luteal phase. At this point your estrogen level starts to decline and the hormone progesterone increases. This can lower your energy level, and make you feel bloated and moody.

These symptoms continue until menstruation, and are most intense in the week before menstruation, which is called PMS (premenstrual syndrome). That’s why in the week before your period starts you may feel particularly vulnerable to stress. Staying hungry for long hours means adding an extra stressor to your life and it may not be the best idea.

During the first few days of the PMS week, you can follow a 14/10 or 16/8 plan. As you approach your period, you can abandon intermittent fasting and eat with a more “normal” pattern, to suit your body.

When you finally have your period, the first few days may also be tough for following an advanced fasting plan, as your body’s energy demands change. Following a less intense plan like the 12/12 or 14/10 fasting plan is ideal.

A few days after your period, your estrogen level starts to increase again and you can go back to your more intense fasting plan. As you will start to feel more energetic, doing high intensity workouts is also ideal during this phase.


Intermittent Fasting and Period Changes

Women who follow strict intermittent fasting plans, involving intense calorie restrictions, or plans that have a very narrow eating window, may experience changes in their menstrual cycle.

This can happen because being hungry for extended periods can affect a part of the brain called the hypothalamus. This is the area responsible for regulating hormones like estrogen and progesterone, which are crucial to ovulation and menstruation.

When the female body faces extreme calorie restriction and doesn’t get the energy it needs, the secretion of gonadotropin-releasing hormone (GnRH) decreases. This decrease is important because GnRH is responsible for releasing two reproductive hormones: luteinizing hormone (LH) and follicle-stimulating hormone (FSH). 

But don’t be intimidated by this information, as these hormonal imbalances and disruption of the menstrual cycle only occur in response to extreme calorie restrictions. Women who follow intermittent fasting diet plans that are suitable for their bodies experience great benefits.

The 12/12, 14/10 and 16/8 plans are usually OK for many women to follow, and some experienced intermittent faster women may follow 18/6 or 20/4 plans. But if a woman is trying to conceive or having hormonal problems, longer fasting hours may make this more difficult and they should consult their doctors before starting fasting.

The most important thing is that women who do intermittent fasting should have a balanced and nutritious diet with enough energy to support their needs.

Intermittent Fasting Plans According to the Menstrual Cycle

  • Day 1-3 of your cycle: 12/12 or 14/10 fasting plans
  • Day 4-10 of your cycle: 14/10 or 16/8 fasting plans (or 18/6)
  • Day 11-15 of your cycle: 12/12 or 14/10 fasting plans
  • Day 16-19 of your cycle: 14/10 or 16/8 fasting plans (or 18/6)
  • Day 20-28 of your cycle (PMS week): fasting not recommended

You can dive deeper into the details of fasting schedules from this article.



Can fasting cause hormonal imbalances?

When following a fasting plan, it’s vital to consume plenty of nutrient-rich calories. If you don’t, your body’s survival mode is triggered, excessive levels of the hormone cortisol are secreted, and your hormones become imbalanced, which can disrupt ovulation. 

As a result, your periods may stop or become irregular. And it can also make getting pregnant more difficult if you’re trying to conceive.

The solution is to consume hormone-balancing foods like anti-inflammatory proteins, healthy fats, and fiber-rich veggies during your eating window, rather than filling your stomach with greasy and sugary junk food.

A nutrition plan that is not so high in calories that you gain weight, but also not so low that you lose ovulation, is recommended for women to maintain balanced hormones without getting fat.

Researchers have defined calorie needs as about 13.6 calories per pound of lean body mass in women. Most womens’ lean body mass is about 70% of their total body weight. For example, if a woman weighs 150 pounds, her lean body mass is around 105 pounds, which means her daily calorie intake should be at least 1,428 calories to avoid hormonal imbalances.


To sum up

If, as a woman, your diet is healthy and balanced, intermittent fasting and your hormones can get along really well. The 14/10 and 16/8 fasting plans are suitable for most women to follow so they can enjoy the benefits of intermittent fasting.

You can change your fasting plan to adapt it to your menstrual cycle. Fasting Kompanion offers different intermittent fasting plans and enables you to create customized fasting plans too.

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