Exercise & Fertility
Exercise and Fertility: What to Know When You're Trying to Conceive
Written by Dr. Fiona Callender, Naturopathic Doctor with a focus in Perinatal Care
A big part of my job is helping simplify and answer your health questions. Many of my patients come in with questions or confusion around things they hear or read on social media. One topic that is rife with conflicting information online is when it comes to exercising while trying to conceive. There’s so much mixed messaging and fear built around this that leaves many patients coming into my office confused and unsure what to do.
We have pretty solid (albeit, basic) guidelines regarding exercise in pregnancy and in weight management prior to becoming pregnant, but we don’t seem to have specific or tangible guidelines for those actively attempting to conceive - whether that’s IVF or unassisted.
When it comes to overall health, we know that exercise reduces the risk of cardiovascular disease and cancer, it improves mood - both depression and anxiety - and improves longevity. In pregnancy, exercise is associated with better outcomes for both mom and baby. All of this is pretty extensively (and conclusively) studied. When it comes to fertility, specifically those struggling with fertility, it seems less clear-cut.
For the average, healthy person, moderate-to-vigorous exercise is generally considered helpful - for most people, exercise improves fertility outcomes. Many folks aren’t exercising enough and even small changes to your routine can make a difference. That said, if you are training for a big event, are an intense cross fitter or an avid runner.. we often need to take a closer look at what you are doing. There have been studies showing higher running volumes with reduced fertility. As a runner myself, I saw this and had an initial sinking feeling.
“That can’t be right!?”
This is the kind of thing that makes it into tik tok and instagram click-bait. We need to pause and not jump to conclusions and think about what’s really happening here. Is it the exercise or is it something else associated with the exercise? High intensity exercise increases our energy needs - and how we balance our energy matters when it comes to fertility.
Understanding energy balance
Energy balance is essentially the calories you take in (food!) minus your expenditure (movement, keeping your organs functioning, being awake etc). Essentially, we need to be eating enough to manage the exercise load we are doing, on top of the energy required to be alive. When we do this, we are OK! There’s no real difference between fertility outcomes in those who exercise vigorously, as long as they manage this balance well.
In 2015 a study came out that highlighted the importance of an energy deficit induced by exercise and how this may be a huge factor in how exercise impacts fertility. The researchers looked at a group of women’s hormones and tracked their menstrual cycle parameters over three months. In a group with a moderate to significant calorie deficit, 85% of them had at least one cycle where their luteal phase was shortened. Anovulation (lack of ovulation) was also more likely in these groups too. In the mild deficit or no deficit groups, there was no real impact on their menstrual cycle. Though this is just one study, it highlights the importance of fuelling for your exercise. You don’t need to be trying to conceive to take this information and apply it to yourself. If you are exercising vigorously… you need to increase how much you eat!
So how does energy impact our hormones?
A luteal phase defect happens when the luteal phase (phase after ovulation to your period) lasts less than 9-10 days. This might also look like irregular bleeding or spotting leading up to your period. This happens when inadequate amounts of progesterone are produced, or your endometrium doesn’t respond as normal to the hormones released. Because progesterone helps support our lining and implantation, this has been associated with struggles with getting pregnant.
As we discussed above, under-eating combined with high intensity exercise can result in this energy deficit. Even 300 calories per day in deficit can result in changes to ovulation and hormonal balance. Some are more sensitive than others. For some people, even really small reductions in calories can disrupt their cycles. My highly active patients and I work really closely on making sure they are eating enough to support their exercise and hormonal goals. Even if your goal isn’t to conceive, fuelling for your sport/exercise is crucial for optimal hormonal (and overall) health.
underlying Hormonal conditions and exercise
What about someone with known conditions impacting fertility? PCOS (polycystic ovarian syndrome) is a good (and well studied) example where we know other factors are often contributing to ovulation challenges.
There is pretty strong evidence that making lifestyle changes that result in metabolic shifts (weightloss being an outcome that is repeatedly studied) results in more pregnancies and consequent babies. These studies often combine diet and exercise so it’s a big challenging to look at exercise as a stand-alone intervention.
Of the studies we have, it seems like as little as 30 minutes of intense exercise three times per week can significantly improve likelihood of conception in those with PCOS. More intense activity seems to reduce ovulatory infertility - even when we control for BMI. That’s a really important point because we are now seeing that the benefits of exercise for fertility in women with PCOS do not appear to be fully explained by weight changes. Frustratingly, I often get women with PCOS in my office who have been left feeling shamed and dismissed by their practitioner when they are simply told to lose weight to manage their PCOS. Weight is very commonly attributed as the cause of their fertility struggles. Though elevated BMI is often a factor in infertility (especially in the research), I think the conversation can often be much more nuanced - especially in conditions such as PCOS. If we can exercise and improve fertility (even with no weight loss) it seems like exercise - for all the amazing benefits it carries - should be a focus and goal.
We know that exercise is beneficial for PCOS symptoms beyond fertility too. Regular exercise impacts testosterone, menstrual cycle length, insulin resistance, and more. We likely need to see about 50 hours of training to see start really reaping those benefits… which means consistency is key! This can take a few months so we need to find something you can stick with.
But what about assisted reproductive technology (ART) cycles? Don’t we have to be careful?
The research shows that exercise improves the number of retrieved eggs and tends to improve outcomes overall in IVF. This is reassuring to many women who have so much fear around this process, but have a strong desire to exercise in order to feel like themselves and cope with stress. That said, every case is unique and it’s always a good idea to ask about your own risks and make a plan with your practitioner. One case where we want to be a bit more cautious is the point in an IVF cycle where you are taking stimulating medication to recruit follicles. In the stimulation phase, our ovaries can get quite large and there is a small increased risk of ovarian torsion. This is a rare but serious complication. Keeping things relatively light in this time is not a good idea (and generally recommended by fertility clinics who are supporting the round of IVF).
When planning your fertility journey, more time spent in higher intensities leading up to trying to conceive - especially before IVF - is probably key. During a medicated cycle, we can back off temporarily, but exercise doesn’t seem to impact implantation or pregnancy when done immediately before IVF.
Key Take aways
Getting started on an exercise routine is beneficial for most of us! How that looks will be unique to what you enjoy and what phase of your journey you are in. Making sure you are balancing your energy well is a key take away, but we don’t need to be fearful of intensity when it comes to exercise. Vigorous exercise helps us manage blood sugar, improve blood flow to our pelvic organs, support our mood and manage stress. If you want more guidance or support, I’m here to help you navigate the confusing fertility/wellness world. If you want to get started on understanding your cycle for fertility, you can download my free fertility tracking guide to get started.
If you would like to get started with one-on-one care and an initial comprehensive health assessment, you can book with me through the link below. I look forward to working with you!