It is true that obesity can lead to lower fertility, and to combat obesity, a combination of diet and exercise is generally recommended. Regular exercise can also lower stress, which is important when you’re trying to cope with infertility. But even with exercise, too much of a good thing can be detrimental in certain situations. How much exercise is too much? And how might too much exercise decrease your fertility? Research can provide some insight.
Research
The research available on exercise and fertility has some inconsistencies. Some studies have found that too much exercise can impede fertility, while others have not found that association. Certain studies that have also found that regular exercise can improve fertility, especially in women who are overweight or have obesity. Since you can’t put people in a lab for years to observe their exercise habits, studies often rely on self-reports from patients. It’s also difficult to pinpoint other factors that may impact fertility. For example, someone who exercises frequently might have different eating habits from someone who doesn’t, and what you eat can also impact fertility.
Exercise Intensity, Duration, and Fertility
When you consider all of the research together, the bulk of the evidence suggests that moderate exercise is beneficial to all everyone and may even improve fertility. However, high levels of exercise might impair fertility, at least in some people. Those conclusions are based on several pieces of evidence.
Aerobic exercise for seven or more hours per week may increase the risk of ovulation problems. Moderate exercise (for more than one hour but less than five hours per week) was found to improve fertility in all women. Strenuous exercise of four or more hours per week may reduce IVF success rates. Vigorous exercise may improve fertility in women who are obese. Vigorous exercise may decrease fertility in women who are at their normal weight.
Exercise Duration
When considering what exercise to limit or cut back on when trying to conceive, research recommends limiting exercise in the vigorous category to less than four hours per week. You would not need to limit moderate exercise. For example, instead of taking a high intensity interval class every day, you could replace some of your workouts with yoga or leisurely walking. You’ll still get to enjoy moving your body, but you won’t be overtaxing your system.
Heavy Exercise
In determining what types of activities might be considered strenuous or vigorous, it may be helpful to consider the intensity in which you participate. For example, some activities like bicycling can be considered moderate exercise, but if you bike very hard, very fast, or on a very hilly route, it could then be considered very strenuous exercise. Aerobic exercise (such as an aerobics class at a gym) can be vigorous, but there are many ways to modify movement to make it easier. Weight training can also be moderate or strenuous depending on the amount of weight you lift, the exercises you choose, and the number of repetitions you complete. Some examples of exercise activities that are more likely to be strenuous include:
CrossFitHigh intensity interval trainingPowerliftingRacquetballRunning
Moderate Exercise
Moderate-intensity exercise is activity that feels sustainable. You should feel like you are breathing more deeply than normal, but you shouldn’t feel breathless. According to the American College of Sports Medicine (ACSM), moderate intensity aerobic exercise occurs when you reach 64% to 76% of your age predicted maximal heart rate (which is calculated as 220 minus your age). You can wear a heart rate monitor or fitness tracker to help you determine if you are in a moderate heart rate zone. Moderate exercise can includes activities like:
WalkingRaking leavesWater aerobicsSwimming lapsBicyclingDancing fast (social)
If You Are Overweight or Obese
While too much exercise can create fertility problems in some women, not getting enough exercise could contribute to obesity. Studies looking at obesity, exercise, and fertility comprehensively have found that for women who need to lose weight, vigorous exercise can actually improve their odds of getting pregnant. So, if you are overweight, you probably don’t need to worry that strenuous exercise will harm your fertility. It’s also valuable to understand that in addition to exercise, diet is also an important factor to consider when you’re trying to lose weight. Reducing junk food and increasing healthy food options, like whole grains, healthy fats, lean proteins, and lots of vegetables, has been found to help with weight loss and improve fertility.
Potential Weight Loss Benefits
Studies suggest that losing just 10% of your current body weight can boost your health and fertility if you are currently obese. Body mass index (BMI) is the measurement used to evaluate someone’s weight based on their height, but you don’t necessarily have to get down to a specific BMI in order to see fertility improvements. Here’s an example. Let’s say a woman is 5’ 4” and weighs 174 pounds. This would give her a current BMI of 30 and place her in the category of being obese. To be at her “healthy, normal weight” on the BMI chart, she’d need to weigh 144 pounds. That would mean losing 30 pounds, which is a lot of weight. However, if she loses just 10% of her weight—about 17 pounds in this example—her fertility would see improvements, despite technically still being considered overweight.
Overall Impact of Exercise on Fertility
Too much exercise seems to impair ovulation in women of normal weight, and there are a few theories on why this happens. For example, one possible result of too much exercise is a luteal phase defect. Despite being a flawed measure, BMI is widely used today in the medical community because it is an inexpensive and quick method for analyzing potential health status and outcomes. The luteal phase is the time period between ovulation and your expected period. This time period, also known as the “two week wait,” is normally between 12 days and 16 days. A shorter luteal phase due to excess exercise can interfere with the ability to get pregnant because it causes progesterone levels to drop. Normally, progesterone levels remain high during this time, which allows a fertilized egg to attach itself to the uterine lining. However, low levels of progesterone can interfere with a fertilized egg implanting, which can lead to infertility. Yet another potential cause for exercise-induced infertility is a change in leptin levels, which regulates appetite and metabolism. If your appetite is low, you may not eat enough, which can interfere with regular ovulation. It’s also possible that women who exercise more than seven hours per week are more likely to restrict their diet. Not eating enough healthy fats, losing weight rapidly, or weighing below the recommended weight guidelines for your height can affect ovulation.
A Word From Verywell
Fertility concerns come with a myriad of emotions that can impact all areas of your life. If you love to exercise, know that you don’t have to give it up completely, but may just want to dial back your intensity if you are not overweight. If you’re still concerned about how to exercise during your fertility journey, your doctor can provide more specific direction tailored to your needs.
