How Much Activity Enhances Fertility? A New Study Says...

Balance is one of the hardest things to achieve in life, and it seems like that's especially true for women who are trying to get pregnant. You know that overall health and fitness play a role in fertility, but you've also heard that there really can be too much of a good thing. Trying to keep up with the "do this, do that" of research data can make you want to throw your hands up and say "I quit!"

Image: Ambro / FreeDigitalPhotos.net 

But you don't have to be an exercise physiologist or a registered dietitian to understand a few simple points amid the building database of knowledge about fertility's connections to weight and physical activity.

And here's the latest: Moderate activity wins the game. Again.

A just-released study (from Fertility & Sterility) of more than 3,000 Danish and U.S. women ages 18 to 40 found that moderate levels of physical activity resulted in "small decreases in time to pregnancy" for women of all body mass index (BMI) levels.

If you're struggling to get pregnant, that finding may not seem so exciting. But factor in the rest of the story and fertility patients may feel a little uplifted by this study.

Importantly, the subjects in this study were drawn from the general population, not from among fertility patients. Requirements of participation included:

• being in a stable relationship with a male partner
• planning to get pregnant
• not receiving fertility treatment

Participants were followed for a year or until they conceived. The researchers looked at several variables, including differences in length of time to conception for women throughout the BMI range. They found that vigorous physical activity either works against you (for women of "normal weight," BMI under 25) or doesn't do anything for you (for overweight or obese women, BMI of 25 or above) in terms of time it took to get pregnant.

In this study, vigorous activity included running, fast cycling, aerobics, gymnastics, and swimming.

The "winners" -- in this case, those who took the shortest amount of time to pregnancy -- were women who engaged in 20 to 39 MET hours (total metabolic equivalents assigned to different kinds of activity) per week of physical activity. And moderate activity was key.

Though the authors concede more data is warranted to investigate different types of physical activity in relation to fertility, their study suggests that overweight or obese women might benefit from any physical activity and lean women will likely enhance their fertility by switching to moderate, rather than vigorous, activity.

So what's moderate?

Brisk walking, leisurely cycling, golfing and gardening.


Source: A prospective cohort study of physical activity and time to pregnancy
             L. A. Wise et al., Fertil Steril 2012