We all know that if you’re trying to get pregnant, it’s important to maintain the general tenets of good health: Eat a balanced diet, get good sleep, lower stress levels, and exercise. But can you have too much of a good thing? Research strongly suggests that yes, too much exercise can hurt your hormonal and general health, and therefore, your fertility.
In a sense, the reproductive organs are the “weakest link” in the pecking order of organs. You know what’s top dog? The brain. The brain will go to any lengths to get what it needs to do what it does. It’s an expensive organ using on average 400 calories a day just to keep you breathing and moving!
The reproductive organs are important, but they aren’t nearly as greedy as the brain is. They are often the first system to shut down when the body senses acute stress. After all, we need to breathe to live. Reproducing is a bit of a luxury when breathing is on the line.
How intense seasons of work affected our ancestors in rural economies—and what it means for you
In On Fertile Ground, A Natural History of Human Reproduction by Peter T. Ellison, he accounts for a phenomenon discovered in farming communities in separate corners of the world . Three examples he provides are the Lese of the Congo’s Ituri Forest, a group of farm women in Southern Poland, and the Tamang of central Nepal. While the landscapes, seasonal weather, and agricultural demands vary across these different groups, they have one definitive thing in common: Ovarian function is lower during the harvesting seasons, when intense metabolic energy expenditure is required. “Low ovarian function” means less frequent ovulation overall, and lowered levels of estradiol and progesterone when ovulation does happen.
It was also observed that fecundity seems to follow this pattern, although this occurrence is far more complex than just hormone levels. Conception rarely occurs during the harvesting season in these communities, but rather before or after it. Incidentally, this helps ensure that calories will be around for the mother to consume after the birth, to help buoy the high caloric needs of a lactating mother. (In fact, a friend of mine had parents who were farmers; he and all four of his siblings were born between late June and end of September, meaning they were conceived after the hard work of the summer harvest.)
You may be thinking “This is cool and all, but I don’t live in a farming community in Nepal, Poland, or the Congo; what on earth does this have to do with me and my desire to get pregnant?”
Here’s the crux of it: The reproductive and endocrine systems are highly sensitive to energy and metabolic conditions, regardless of where you live and why you’re expending calories. In other words, if you are spending too much energy (like on a really rigorous workout multiple times a week), the body will sense that there’s not enough energy to make a baby. The result? Lower ovarian function and less fecundity.
How much exercise is too much when you’re trying to get pregnant?
A 2012 study found evidence for a dose-response relation between increasing vigorous physical activity (PA) and delayed time to pregnancy (TTP) in all subgroups of women . But what, exactly, is “vigorous” PA? According to this study, intense physical exercise performed for greater than five hours a week is “vigorous physical activity.” Interestingly, less than five hours but more than one hour a week of vigorous PA had a positive relationship with TTP regardless of a woman’s body mass index (BMI). The study concludes that “some scientists postulate that the effect of PA on fertility may be positive up to a certain level of activity, and then have a deleterious effect above that threshold level of activity.”
It has been long known that athletes are more prone to anovulation. And when you stop to think about it, it makes sense. Pregnancy and lactation are biologically expensive ventures. The body would have a vested interest in making sure there is more than enough energy to go around before setting out on this enterprise. The equation is simple: When there’s enough calories and energy available, fertility (and ovarian function) is high. When there’s not, it’s low.
Prioritizing metabolic energy for fertility, conception, and pregnancy
So what does this mean for the modern woman trying to conceive in a post-industrial economy? Fertility and conception are highly individualized, but it’s a good rule of thumb to pull back on your exercise regimen if it’s an intense one and you’re trying to get pregnant. But no one can make the blueprint for the “perfect” workout other than you.
You know your needs better than anyone. But it is fair to say that our culture glamorizes intense workouts, little to no fat stores (which are super important for women, especially at the outset of a pregnancy), and lower calorie loads–all of which can make it harder for the average woman to get pregnant.
It shouldn’t be any surprise but the answer to the “optimal” amount of exercise for fertility is probably somewhere in the middle of couch potato and Instagram fitness influencer. It’s important to move your body and exercise both before, during, and after a pregnancy. But when you boil it down to a metabolic formula, the body needs some extra calories, fat, and energy to gestate and lactate.
The best kind of workout for trying to conceive
If you’re trying to conceive (or pregnant or postpartum), keep exercise moderate and mellow to something like walking, swimming, or gentle yoga. Mild strength training is more important than cardio during these reproductive seasons. Reproductive demands on the body are intense, and they don’t stop when the baby is on the outside! I always chuckle at the “exercise you can do while wearing your baby;” as if baby wearing itself isn’t a workout.
If you’re trying to conceive and currently in the midst of an intense exercise regimen, consider asking yourself why you started the regimen in the first place: Was it to get healthier so that you could conceive? Was it for mental and emotional health benefits? Was it maybe–at least somewhat–because you’ve internalized some of the ideas our culture has about body shape and image? If getting pregnant is really important to you, what can you adapt about your current regimen that will allow you to keep whatever benefits you’ve witnessed, while still preserving your fertility?
The best way to think of the exercise and fertility calculus is a simple mathematical equation with the variables of energy and calories. Menstruating and conception are hugely expensive in terms of energy. By mellowing out your workouts a bit, this will give your body a little more energy to conceive. And don’t worry about counting calories, because your body will need a little bit extra of those too!
 Ellison P. On Fertile Ground. Cambridge, MA: Harvard University Press; 2003.
 Wise, L., Rothman, K., Mikkelsen, E., Sorensen, H., Riis, A. and Hatch, E., 2012. A prospective cohort study of physical activity and time to pregnancy. Fertility and Sterility, [online] 97(5), pp.1136-1142. Available at: <https://www.fertstert.org/article/S0015-0282(12)00259-2/fulltext> [Accessed 30 June 2021].