Fasting has become increasingly popular for its potential health benefits, but many people who menstruate are left wondering how it might affect their cycle. The menstrual cycle is driven by a delicate hormonal balance and as such, disrupting this balance can result in irregular periods, increased pain, or changes in flow.

For anyone considering fasting, understanding its potential effects on their cycle is a vital part of making an informed decision.

In this article we explore how fasting might impact the hormonal system that governs menstruation and provide guidelines for fasting that consider the menstrual cycle.

So, Should Women Fast? You Ask.

Short answer: Yes, if you are generally healthy and mindful of what phase of your cycle you are on.

Essentially, since menstrual cycle relies on hormones like estrogen and progesterone, the issue with fasting arises as these hormones can be sensitive to significant changes in caloric intake or stress levels.

Overly restrictive fasting or prolonged fasting periods can disrupt this balance, potentially leading to irregular cycles, hormonal imbalances, or increased stress on the body.

By adopting more gentle fasting methods, such as intermittent or modified fasting, and tailoring the approach to different phases of the menstrual cycle, women can enjoy the benefits of fasting while minimizing risks to their hormonal health.

Fasting Methods and Their Impact on the Menstrual Cycle

As mentioned above, fasting comes in various forms, each with unique effects on the body. For those with a menstrual cycle, intermittent fasting (IF) and modified fasting are generally the most suitable options, as they are less likely to cause a significant hormonal disruption. Here’s a quick overview of common fasting methods:

Intermittent Fasting (IF): 

Involves alternating periods of eating and fasting, such as the 16/8 method (16 hours fasting, 8 hours eating). This flexible and customizable approach is often the easiest to align with hormonal needs.

Modified Fasting

Allows for limited calorie intake or specific foods during fasting periods. This less extreme approach helps maintain energy levels and hormonal stability.

Time-Restricted Eating (TRE):

Similar to IF, TRE restricts eating to specific hours of the day (e.g., a 10-hour window), working with the body’s natural circadian rhythms for a gentler fasting experience.

Water Fasting:

Consuming only water for 24+ hours. While it may support cellular cleansing (autophagy), it can be overly stressful for those with a menstrual cycle and is best avoided.

Extended Fasting:

Lasting several days or weeks, this highly restrictive method is not recommended for most people, especially those with menstrual cycles, as it can significantly disrupt hormone levels.

In the next section, we’ll explore how to incorporate these fasting methods throughout your menstrual cycle to align with your body’s natural rhythms and support hormonal balance.

Optimal Fasting Based on Your Menstrual Cycle

The main things to consider when fasting if you have a menstrual cycle are

1. When you are fasting.
2. What type of fasting you are doing.

1. Follicular Phase (Day 1 to Ovulation)

What’s Happening: The follicular phase starts on the first day of your period and ends with ovulation. Estrogen levels gradually rise, while progesterone remains low. Energy levels tend to be higher during this phase.

Best Fasting Practices:

• Type of Fasting: Intermittent fasting (e.g., 14-16 hours) can work well during this phase, as your body is more resilient to stress and blood sugar regulation tends to be better.
• Foods to Focus On: Include nutrient-dense, whole foods with complex carbs, lean proteins, and healthy fats to support estrogen production and energy levels.
• Why It Works: Estrogen helps stabilize energy and mood, making this phase an ideal time for more structured fasting or slightly longer fasting windows.

2. Ovulatory Phase (Around Days 12-16)

What’s Happening: Ovulation marks the peak of estrogen levels, while testosterone also rises briefly, boosting energy and confidence.

Best Fasting Practices:

• Type of Fasting: If you feel energetic, you can continue moderate intermittent fasting (12-14 hours), but avoid extreme fasting (e.g., 20:4 or multiple days).
• Foods to Focus On: Support ovulation with anti-inflammatory foods like leafy greens, berries, omega-3-rich fish, and seeds (e.g., pumpkin or flax).
• Why It Works: Your body is still resilient to stress, and fasting can be well-tolerated as long as it isn’t extreme.

3. Luteal Phase (Post-Ovulation to Menstruation)

What’s Happening: Progesterone rises, and your body prepares for a potential pregnancy. Energy levels may fluctuate, and you might experience PMS symptoms such as fatigue or cravings.

Best Fasting Practices:

• Type of Fasting: Reduce fasting intensity. Stick to shorter fasts (12 hours or less) or avoid fasting altogether if you feel low energy or have strong cravings.
• Foods to Focus On: Prioritize nourishing, grounding foods like sweet potatoes, avocados, nuts, and dark chocolate to support progesterone production and curb cravings.
• Why It Works: The luteal phase can be more stressful on your body, and intense fasting may exacerbate fatigue or hormonal imbalances. Shorter fasts help maintain stability.

4. Menstrual Phase (Days 1-5 of Your Period)

What’s Happening: Estrogen and progesterone levels are at their lowest, which can lead to fatigue or a need for more nutrients.

Best Fasting Practices:

• Type of Fasting: Avoid fasting during your period or stick to very light fasting (e.g., 10-12 hours). Focus on eating nourishing meals to replenish lost nutrients.
• Foods to Focus On: Iron-rich foods (e.g., spinach, lentils, red meat), magnesium (e.g., dark chocolate, nuts), and hydrating foods to support recovery and reduce fatigue.
• Why It Works: Your body needs more nutrients during menstruation, and fasting can add unnecessary stress during this time.

How Hormones Beyond Estrogen and Progesterone Are Impacted by Fasting

1. Insulin and Blood Sugar: One of the first hormonal responses to fasting is a decrease in insulin levels. During fasting, the body becomes more efficient at using stored glucose for energy, leading to lower blood sugar levels. These fluctuations in insulin and blood sugar can influence other hormones, potentially affecting the regularity of the menstrual cycle.
2. Leptin: Leptin is a hormone produced by fat cells that helps regulate appetite and metabolism. Prolonged fasting and extreme calorie restriction can lead to reduced leptin levels. Low leptin can signal to the body that it's in a state of energy deficiency, potentially affecting the hypothalamus and, subsequently, the menstrual cycle.
3. Ghrelin: Ghrelin, often referred to as the "hunger hormone," increases during periods of fasting or calorie restriction. Elevated ghrelin levels can trigger feelings of hunger and discomfort, which may be particularly pronounced during fasting, impacting the overall well-being of individuals who menstruate.
4. Cortisol: Fasting can lead to increased cortisol production, often referred to as the "stress hormone." Elevated cortisol levels can have widespread effects on the body, potentially contributing to hormonal imbalances that impact menstrual health.
5. Thyroid Hormones: Thyroid hormones, including thyroxine (T4) and triiodothyronine (T3), play a crucial role in metabolic regulation. Fasting may lead to changes in thyroid hormone levels, which can affect energy expenditure and overall metabolism, potentially influencing the menstrual cycle.

Pro’s and Cons of Fasting for Women

While there are ways that you can safely fast, given that it also comes with inherent risks, here we examine both the potential benefits and risks of fasting during menstruation:

Potential Benefits of Fasting

• Improved Metabolism: Some research suggests that intermittent fasting and time-restricted eating may enhance metabolic function, potentially aiding in weight management and insulin sensitivity.
• Autophagy: Fasting can trigger autophagy, a cellular process that removes damaged components and may have longevity and health benefits.
• Weight Management: Fasting can create a caloric deficit, which, when done sensibly, can contribute to weight loss and body composition improvements.
• Mental Clarity: Some individuals report improved mental clarity and focus during fasting periods, which can enhance productivity and cognitive performance.

Risks

• Hormonal Disruptions: Fasting can disrupt hormonal balance, potentially leading to menstrual irregularities, amenorrhea, and changes in hormonal profiles like estrogen and progesterone.
• Nutritional Deficiencies: Prolonged fasting without proper nutrition can result in deficiencies in essential nutrients, which can exacerbate menstrual discomfort and overall health issues.
• Stress and Emotional Well-Being: Fasting, especially when combined with the stress of menstrual discomfort, can impact emotional well-being, potentially leading to mood swings, irritability, or emotional instability.
• Impact on Fertility: Amenorrhea resulting from fasting can have implications for fertility, as ovulation may be disrupted. Fertility concerns should be considered if you're planning to conceive in the future.

Given these potential benefits and risks, it's important to approach fasting during menstruation with careful consideration and awareness of your body's signals. 

Tips for Fasting Safely

General Tips for Fasting with a Menstrual Cycle

1. Listen to Your Body: Adjust fasting based on how you feel. If fasting exacerbates symptoms like fatigue, cravings, or mood swings, ease up.
2. Stay Flexible: Hormonal shifts can vary from cycle to cycle, so adapt your fasting routine as needed.
3. Avoid Extreme Fasting: Prolonged fasting or very restrictive eating can disrupt the delicate hormonal balance necessary for a healthy cycle.
4. Hydrate Well: Proper hydration is essential during fasting, especially during menstruation.
5. Consult a Professional: If you have irregular cycles, PCOS, or other hormonal conditions, consult a healthcare provider before starting a fasting routine.

Fasting for Women: What You Should Know (FAQs)

Intermittent Fasting for Women

Intermittent fasting (IF) is a popular approach to eating, but women need to be more cautious than men when trying it. Hormones like estrogen and progesterone play a big role in metabolism and reproductive health. Because of this, fasting can affect women’s cycles differently.

Some women may notice changes like irregular periods or even missed ovulation if their fasting routine is too strict. It’s important to pay attention to your body and start with a gentle fasting method to see how it affects you.

Should Women Post-Menopause Fast?

Women who are post-menopause may have a different experience with fasting since they no longer have menstrual cycles. With lower estrogen levels, fasting can sometimes help improve metabolic health, reduce inflammation, and support weight loss. 

Even without monthly cycles, it’s still important to pay attention to your body’s signals. Post-menopausal women should focus on maintaining balanced nutrition and avoiding nutrient deficiencies to stay healthy while fasting. Checking in with a healthcare professional is always a good idea when trying a new eating pattern.