Written and medically reviewed by Katya Meyers, RD
Infertility affects up to 1 in 6 couples worldwide, according to data from the World Health Organization (WHO). Infertility stems from a range of factors, including hormonal imbalances, lifestyle choices, and increased parental age. While traditional treatments for infertility include medication, surgery, and assisted reproductive technologies, recent research suggests that intermittent fasting may also have a positive impact on fertility. While researchers are still working to understand the links, possible targets of action include reproductive hormones, ovarian function, and sperm quality.
What Is Intermittent Fasting for Fertility?
Intermittent fasting (IF), or time-restricted eating, has gained popularity as a strategy for weight loss and improving metabolic health. The concept of IF involves periods of restricted caloric intake, alternating with periods of normal eating. There are several variations of IF, including the 16:8 method, alternate-day fasting, and the 5:2 diet, and it may take some experimentation to determine which style of fasting is right for you. While the primary focus of IF has been on its beneficial effects on metabolic health, longevity, and autophagy, recent research has suggested that IF may also have other health benefits, including increased fertility.
If you’ve been curious about intermittent fasting, but searching for the motivation to begin your fasting habit, learning more about the ways fasting can improve fertility is a great place to start. Trying an intermittent fasting diet is a good way to implement healthy lifestyle changes.
Can Intermittent Fasting Improve Fertility?
While everyone responds to fasting a little differently, the reality is that every time you fast, it kickstarts a chain of physiological changes that can improve your metabolic health. For example, overwhelming evidence suggests that intermittent fasting can improve insulin resistance and promote weight loss. Maintaining a healthy BMI and good insulin sensitivity is important for optimal fertility, as both obesity and insulin resistance have been linked to delayed conception, poor egg quality, and increased risk of miscarriage. Obesity and insulin resistance are also risk factors for conditions like polycystic ovarian syndrome (PCOS), one of the main causes of infertility.
Intermittent fasting also helps to reduce inflammation levels in the body. Chronic inflammation has been linked to a range of health problems, including infertility. Inflammation may be caused by obesity, disease, a diet high in processed foods, and other factors. Fasting can reduce your inflammation levels and improve your fertility.
How Does Intermittent Fasting Affect Female Reproductive Hormones?
The menstrual cycle is regulated by a complex interplay of hormones, including follicle-stimulating hormone (FSH), luteinizing hormone (LH), estrogen, and progesterone. One of the ways that IF may improve fertility is by encouraging optimal levels of reproductive hormones, particularly in women with PCOS — a primary cause of female infertility.
One new study evaluating the effect of a 16:8 TRF (or a 16-hour fasting window and an 8-hour eating window) in women with PCOS showed a normalization of androgen levels and improved insulin resistance, as well as a reduction in BMI and body fat percentage. These changes resulted in improvements in menstrual cycle irregularity in 73% of study participants, and benefits were increased when the majority of food was consumed earlier in the day.
In women without PCOS, the picture is more complicated, and more research is needed. That said, much of the concern regarding the effect of IF on reproductive hormones in women stems from a 2013 rodent study. While the study of young female rats did demonstrate a negative effect on fertility hormones, there are a few important caveats:
- The rats were fed only once per day on alternate days, which is a very restrictive eating pattern.
- This fasting protocol resulted in a 19% reduction in body weight over the course of 12 weeks.
- The rats were 3 months old, equivalent to approximately 9 years old in human years.
More recent human research of 16:8 TRF in pre and postmenopausal women demonstrated no reduction in estrogen, progesterone, and sex-binding globulin hormone (SBGH) levels, though DHEA levels did decline slightly. However, it is important to note that this research was done only in obese females, and more research is still needed.
Does Intermittent Fasting Affect Male Fertility?
IF may also have a positive impact on sperm quality in men. Studies have shown that IF may improve sperm quality by reducing inflammation and oxidative stress, which can damage sperm DNA and lead to poor sperm quality. Additionally, one study on sperm motility demonstrated a significant difference in sperm motility after just one week on a healthy diet, which, similar to time-restricted eating, lowered blood-sugar levels.
Other Ways IF May Support Fertility
Weight Loss
Obesity is a known risk factor for infertility and pregnancy complications, with an optimal BMI being in the range of 19–25. Practitioners recommend lifestyle modifications, such as intermittent fasting, that can lead to preconception weight loss. That said, while being at a healthy body weight is ideal, studies show that even small decreases in weight can improve maternal, fetal, and newborn health. Time-restricted feeding has proven to be an effective tool in long-term weight loss.
Improved Overall Health
Intermittent fasting can help you live a longer and healthier life. Among the many benefits of IF, it can help you lose weight, improve body composition, and lower cholesterol and insulin levels.
Better Sleep Quality
Intermittent fasting has been linked to improved sleep quality in as little as one-week study period. Fasting can help align your circadian rhythm and improve sleep quality. One study on time usage in the United States concludes there is good reason to end your eating 2–4 hours before bed, as doing so can improve sleep efficiency and duration. Better sleep hygiene reduces stress and lowers rates of sexual dysfunction, both of which can improve fertility.
Can You Do Intermittent Fasting While Trying to Conceive?
Moderate forms of intermittent fasting, such as a 12:12 fast, are likely safe for almost anyone, including those trying to conceive. Many people do this anyway, even without time-specific restrictions. And, if you have a very high BMI or PCOS, you may benefit from spending a longer amount of time in a fasted state each day, such as through a 14:10 or 16:8 fast.
However, it isn’t always the right time to start fasting. And if you are trying to conceive, you should definitely speak to your doctor or reproductive practitioner before making any significant changes to your nutrition or exercise regimen. This includes starting intermittent fasting.
Fasting is NOT recommended for women who:
- Are currently pregnant
- Are breastfeeding
- Are underweight
- Have a history of eating disorders
What Is the Best Intermittent-Fasting Plan for Fertility?
There is no one best intermittent-fasting plan for fertility. This is partly due to individual physiology (what works for your body doesn’t necessarily work for someone else’s) and partly due to the fact that research is still ongoing. To date, much of the research has been done in animals with differing metabolic needs and physiology, making it difficult to translate exact fasting protocols to humans. For this reason, employing a relatively conservative approach to fasting (particularly for females) that allows for some variability should be employed. TRF (time restricted feeding) is an approach that allows for flexibility, and can be a good place to start your fasting journey.
A gentle 12:12 (12 hours of fasting with a 12-hour eating window) aligned with your circadian rhythm may be the best way to begin. Building slowly to a 14:10, or potentially even a 16:8, eating pattern, with approval from your healthcare provider, can be a safe and effective approach, but it depends on your specific physiology and health status.
A fasting regimen is best followed for at least two months for the positive hormonal effects to take hold, and during those months, it’s not recommended to fast for the final 8 days of your cycle.
Mistakes to Avoid When Intermittent Fasting for Fertility
Not Consuming Enough Calories
While IF can lead to weight loss and improve metabolic health, it can also lead to a decrease in calorie intake. If you’re not trying to conceive in the short-term, this may be a good thing, depending on your health goals. However, since your body is evolutionarily designed to prevent pregnancy during times of chronic food shortage, not eating enough can actually hurt your chances of conceiving.
That’s because ovulation and pregnancy are metabolically expensive processes, which require sufficient energy to occur. It is important to avoid severe caloric restriction. Studies show that women with BMI below 19 are more likely to experience difficulties with fertility, including lower oocyte (egg) quality. Research indicates that insufficient energy and low body fat and/or weight can cause your menstrual cycle and ovulation to become irregular — or even halt altogether — making it more difficult to become pregnant. When fasting for fertility, it is important to eat enough during the eating window to maintain proper reproductive function. If you are already at or below an ideal body weight, spending too much time in the fasted state can have negative side effects, such as increased cortisol levels that may have downstream effects on reproductive hormone production.
Eating the Wrong Foods
It is important to eat a diet rich in high quality, whole foods to prevent nutritional deficiencies, especially when fasting for fertility. Studies indicate that the relationship between diet and fertility is inextricable, and sufficient micro and macronutrients are needed for optimal reproduction. A low level of folic acid, for example, has been linked to lower rates of live births. When it comes to male fertility, compelling research shows that sperm motility is improved after just one week on a healthy diet. A varied diet, replete with a variety of fruits, vegetables, high quality proteins, fats, and carbohydrates, plus a prenatal vitamin, will help ensure that your diet is nutritionally balanced.
Over-Exercising
Similar to undernutrition, over-exercising can also put your body in a state of negative energy balance. While some exercise is definitely a good thing, too much can induce stress on the body, which increases the risk of infertility, particularly if you are also combining intense exercise with periods of fasting. Research has shown that excessive exercise can disrupt the delicate balance of hormones needed for reproductive function, leading to irregular menstrual cycles, anovulation, and decreased fertility.
Specifically, one recent study found that women who engaged in the highest levels of vigorous exercise had a 42% increased risk of infertility compared to those who did not exercise at all. Furthermore, intense exercise can also lead to a decrease in body fat; if levels are too low, it can have a negative impact on the production of estrogen, a hormone critical for female reproductive health. Therefore, it is important to maintain a healthy exercise routine and avoid over-exercising to promote optimal fertility.
Not Drinking Enough Water
Maintaining good hydration is a good idea, not just for feeling good while you fast, but also for maximizing your chances of a healthy pregnancy. Research shows that dehydration during pregnancy is associated with higher levels of complications, including preterm births, and is important for maximizing the chance of conception. Dehydration has been linked to lower sperm volume and quality in males. And, in females, dehydration can result in poor egg health and less mucus secretion, which can help transport the sperm to the fallopian tubes.
Conclusion
Intermittent fasting can be a simple and effective approach to improving your fertility, especially if you are overweight or obese or suffer from polycystic ovary syndrome. Although the science is evolving, more research is needed before recommending intermittent fasting, carte-blanche, to those who are trying to conceive in the short-term. However, for those who are looking to optimize their health and longer-term reproductive fitness, the benefits of intermittent fasting are significant. Getting started with intermittent fasting may not always feel easy, but building gradually into a fasting habit can support your long term health and reproductive goals.
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