Can Fasting Affect Fertility? What Women Need to Know

Fasting and time-restricted eating (TRE) have gained tremendous popularity for their potential health benefits—from improving metabolic health to enhancing longevity. But when it comes to female fertility, the effects are not so straightforward. For women trying to conceive, fasting can either be a powerful tool or a disruptive stressor. Understanding the nuances is essential for making informed decisions about your reproductive health.

Why Women Are Often Left Out of Fasting Research

Most fasting studies are done on men or postmenopausal women, in part because the hormonal fluctuations of the female cycle are seen as a "confounding variable" that would skew results. As a result, much of what we know about fasting comes from a male-centric view of metabolism. But women are not small men. Their hormones influence everything from metabolism and fat storage to appetite and reproductive health—so we can’t simply apply male-based research to female bodies.

“Females have a distinct hormonal environment that responds differently to caloric restriction and fasting,” says Dr. Felice Gersh, OB/GYN and author of PCOS SOS.

In fact, one of the only mouse studies on alternate-day fasting in females showed disrupted reproductive cycles, reduced ovary size, and lowered levels of key reproductive hormones like luteinizing hormone and estradiol (Williams et al., 2021).

How Fasting Might Support Fertility

For some women, especially those struggling with insulin resistance or polycystic ovarian syndrome (PCOS), intermittent fasting can offer meaningful benefits. PCOS is one of the most common causes of infertility, and it’s strongly linked to insulin resistance. By lowering insulin levels, fasting may improve ovulatory function and hormone balance.

A 2021 review in Nutrients found that intermittent fasting could reduce insulin resistance and inflammation—both of which are key contributors to PCOS-related infertility (1).

Similarly, a 2016 study in Cell Metabolism showed that early time-restricted feeding improved insulin sensitivity, blood pressure, and oxidative stress markers in prediabetic men and women (2).

How Fasting Might Harm Fertility

For other women, especially those with low body fat, high stress levels, or pre-existing cycle irregularities, fasting may do more harm than good. Extended fasts or chronic caloric restriction can lead to hypothalamic amenorrhea—a condition where the brain stops signaling the ovaries to ovulate.

This occurs because the hypothalamus, which regulates reproductive hormones, is sensitive to perceived energy availability. If the body senses food scarcity, it downregulates reproductive function as a survival mechanism. A study published in Frontiers in Endocrinology found that energy deficiency—even without full-blown eating disorders—can disrupt the hypothalamic-pituitary-gonadal (HPG) axis and halt ovulation (3).

Women athletes and those under chronic stress are particularly at risk. Cortisol, the body’s primary stress hormone, competes with progesterone for hormone-building resources. This hormonal imbalance can lead to luteal phase defects and anovulation.

Not All Fasts Are Equal

A moderate fasting window (12–14 hours overnight) may be well tolerated by most women, especially if it aligns with natural circadian rhythms. However, longer fasts (16+ hours), especially if practiced daily, can strain female hormonal systems.

Studies suggest that women respond differently to fasting than men, with increased reports of menstrual disruptions in prolonged fasting protocols (4). Yet, much of the clinical literature on fasting excludes women of reproductive age due to the "confounding" variable of hormone fluctuations. Ironically, this is the exact population where we need better data—because their hormones make outcomes more variable and more relevant.

Signs You Should Pause Fasting

If you’re experiencing any of the following while fasting, this may indicate that fasting may not be the right choice for your current health status:

• Irregular or missing periods

• Low libido

• Fatigue or brain fog

• Feeling cold all the time

• Hair thinning or loss

  
  

These can be signs of an energy deficit that’s negatively impacting reproductive function.

The Bottom Line: Personalization Over Protocol

Fasting is not inherently good or bad for fertility—it’s all about context. For women with PCOS and insulin resistance, TRE may enhance hormonal balance and improve ovulation. For women already in a delicate hormonal balance, fasting could tip the scales in the wrong direction.

If you’re trying to conceive, it’s essential to work with a provider who understands female physiology and can tailor recommendations to your individual health status, lifestyle, and cycle health.

Sources:

1. Viana, L. R. et al. (2021). Intermittent Fasting and Metabolic Health: An Emerging Paradigm. Nutrients, 13(9), 3179. https://doi.org/10.3390/nu13093179

2. Sutton, E. F. et al. (2018). Early Time-Restricted Feeding Improves Insulin Sensitivity, Blood Pressure, and Oxidative Stress. Cell Metabolism, 27(6), 1212–1221. https://doi.org/10.1016/j.cmet.2018.04.010

3. De Souza, M. J. et al. (2014). Hypothalamic Amenorrhea and Energy Availability. Frontiers in Endocrinology, 5, 1–16. https://doi.org/10.3389/fendo.2014.00146

4. Michalsen, A. (2019). Prolonged fasting in humans: scientific update and clinical applications. BMJ Nutrition, Prevention & Health, 2(1), 67–73. https://doi.org/10.1136/bmjnph-2019-000012

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