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Are your fitness goals helping or hurting your fertility: An Evidence-Based Look at 5 Common Practices

drtanyawilliams - September 27, 2023 - 2 comments

If you’re looking to get pregnant whilst following a fitness plan, you may have questions about how your fitness choices could impact your fertility. 

If this sounds like you, you’re in the right place! Based on some of the most frequently asked questions about the intersections of health/fitness practices and fertility, we did a mini deep-dive into a few key practices to bring you the latest findings. 

Our goal in this post is to give you some key data points that will start to answer your questions about how common health/fitness practices could affect your fertility, as a male or female. 

Read on for the latest fertility findings on intense exercise, intermittent fasting, protein powder, creatine, and anabolic steroids.

Preamble – Weight and fertility

Before we go any further, it’s important to address what weight, health, and fitness have to do with fertility in the first place? The links may be stronger than you think. 

Firstly, being overweight or obese can significantly affect fertility and the chance of natural conception. For women, being overweight or obese could dysregulate the menstrual cycle and cause other health issues which make it more challenging to get pregnant. Research has shown that for women in these categories, losing weight has increased their spontaneous conception rate and decreased their need for further fertility treatment. For men, obesity can reduce the overall quality of sperm. 

On the other side of the coin, being underweight (having a BMI of 18.5 and under) can also make conception harder. This is because, when you’re underweight, your body may stop producing estrogen, which can also dysregulate the female menstrual cycle and stop the body from ovulating or menstruating.

Intense exercise

A muscular blonde woman in shorts and a sports bra holds weight ropes in a squat position at the gym.

While we rarely discourage healthy and moderate exercise, we want to raise a yellow flag here.  If you’re setting big fitness goals based on intensive exercise, you may want to consider the potential effects on your fertility if you’re hoping to conceive at the same time. Let’s consider the evidence by sex:

In women, we’re missing research to fully understand how intense exercise affects fertility. Observational studies have shown that intense exercise disturbs ovulation, but short-term studies that have been done have not always found the same. With mixed results, we’re not sure how long-term training and chronic energy deficit impact women’s fertility.

For men, amongst recreational athletes, exercise appears to have a positive or no effect on fertility. But amongst professional athletes, intense exercise could negatively impact sperm concentration, % of motile spermatozoa, and % of morphologically normal spermatozoa. This said, researchers can’t be sure how these factors impact the ability to conceive. 

Intermittent fasting

As you build your fitness plan, it may include a nutrition regimen, like intermittent fasting. Intermittent fasting, or time-restricted eating, is a practice wherein you consume all your food and caloric drinks during a set time window in a day, while fasting outside of that window. It’s becoming a popular method for people to control their weight, and even has some evidence of reducing the risk of metabolic diseases like diabetes.

But does intermittent fasting affect fertility? Since there is little research on this correlation, the jury may still be out. From what research has been done, there’s a chance that intermittent fasting could lower androgen markers in both females and males. If so, the practice could help treat hyperandrogenism in females with polycystic ovarian syndrome (PCOS), improving menstruation and fertility. But in males, reducing androgens could reduce libido and hurt metabolic health. Still, more research is needed to confirm these early findings. 

Protein powder

A young woman in leggings and a sports bra scoops protein powder into a water bottle in a modern kitchen.

The past decade has seen the rise of protein powder, not just for bodybuilders, but for anyone looking to supplement protein in their diet. If this is you and you’re planning on or trying to conceive, you might be wondering, does protein powder affect fertility?

One important consideration is the hidden ingredients in your protein powder. Since protein powders are not listed as medical drugs but as dietary supplements, the testing and standards are far less rigorous. So if you’re buying supposedly “pro-androgenic” supplements (not necessarily your common whey or soy protein) the product you buy may be contaminated with other problematic ingredients. A recent study found that 23 of 24 dietary supplements sold in fitness equipment and online stores contained anabolic steroids. 

The impacts on fertility? We haven’t seen enough research done on women to make a statement. As for men, a 2018 study amongst 20 subfertile men found that avoiding protein supplements was linked to improved sperm concentration, although there was no significant impact on total sperm count. The researchers behind the study suggest the potential benefit of discouraging protein supplements in oligozoospermic men who are in fertility treatment. But there is not yet enough research on how protein supplements could affect the reproductive health of the many young men who consume them. 


You may have heard some fitness gurus advocate for supplementing creatine to gain muscle and support your fitness goals. Creatine is an amino acid derivative made from arginine, glycine and methionine. While many people have wondered if supplementing creatine is safe, the International Society of Sports Nutrition claims that using it as a nutritional supplement within established guidelines is safe, effective, and ethical. But how does creatine affect fertility? 

In women, there are a few points to be made. Since creatine acts as the substrate for the creatine kinase system, which is evidenced to operate in certain layers of the uterus, it likely plays a role in reproduction. Positive or negative? 

Some studies have associated creatine metabolism disturbances with poorer fertility and pregnancy outcomes. On the other hand, researchers have studied whether supplementing creatine during pregnancy could help protect against hypoxia-induced perinatal injury, especially in the brain. But it’s not clear if creatine is an essential element for successful reproduction. More research around how the uterus metabolizes creatine could help us discover ways to combat poor embryo implantation and the inability to conceive, while also enhancing the uterus’ contractile performance while giving birth.

Creatine is gaining popularity amongst men for its potential fertility boosting power because of its role in sperm energy metabolism. Since spermatozoa are cells that need energy, they can struggle with deficient creatine metabolism. This is why poor sperm count and motility are often linked to low levels of creatine. Pilot trials have observed that taking a creatine supplement seems to improve sperm quality. This preliminary evidence suggests that creatine could actually help reduce subfertility in men. 

Anabolic steroids

A young, dark-haired man in a grey tank top flexes his large right bicep at the gym.

Albeit a much more intense fitness practice, anabolic-androgenic steroids are still common enough (3 million users reported in the US) that it’s important to mention them. 

For some people, combining a good diet and intense exercise plan with anabolic steroids allows them to increase their strength and muscle mass. The problem is that anabolic steroids are by nature androgenic and have many side effects, from mild and reversible, to potentially fatal and permanent. When anabolic-androgenic steroids (AAS) are abused, they are often linked to short- or long-term male fertility impairment.  

Many men who use these steroids do not realize the long-term impact they could have on their fertility. If you are using anabolic steroids, we recommend that you stop immediately, not just for your overall health, but also for your fertility.

Final thoughts

We’ve given you a brief overview of a few common fitness interventions and how they might impact your fertility, based on the currently available scientific evidence. As you may have noticed, many of these topics are not yet studied enough to have conclusive evidence, so it can be hard to know what to listen to.

If you’re working towards fitness and health goals, what we can recommend is to do your own research from multiple credible sources. It’s always a good idea to talk to your doctor before you make any changes to your lifestyle, especially if you’re planning to conceive.

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