Is Too Much Exercise Hurting My Chances of Conceiving?

Screen Shot 2016-02-11 at 4.14.45 PM

When people think of being healthy, one of the first thing that comes to mind is exercise. It’s good for you, gets your heart pumping and blood flowing, but if you are having trouble conceiving, is too much of a good workout a bad thing?

“We’ve known that weight is an important factor in fertility, but considering the role of exercise is a recent phenomenon in Western medicine,” explains Robert Brzyski, MD, PhD, professor of obstetrics and gynecology at the University of Texas Health Science Center at San Antonio . “Unless a woman’s periods are absent or irregular, exercise is usually the last variable we look at, because it’s the one we know the least about and one whose effect varies from woman to woman,” he says. “But research is beginning to suggest it’s more important than we realize.” Preliminary research suggests that regular workouts may actually improve reproductive function: A study in Obstetrics & Gynecology concluded that women who exercised 30 minutes or more daily had a reduced risk of infertility due to ovulation disorders. On the other hand, some data links too much vigorous exercise with lowered fertility, as both a 2009 study in Human Reproduction and a Harvard study of elite athletes found.

With so little to go on, and what there is sounds confusing, it’s no surprise women’s-health organizations don’t provide doctors with any specific rules on exercise frequency or intensity for women trying to conceive.

Let’s start with the ideal weight to conceive:

The numbers on your scale can also be key to your ability to conceive. Exercise, of course, can help regulate your weight, but only if you’ve got a realistic grip on the numbers. According to a 2010 University of Texas Medical Branch at Galveston study, nearly 48 percent of underweight, 23 percent of overweight, and 16 percent of normal-weight reproductive-age women don’t accurately assess their own body weights. Such a mis-perception could have an impact on your health habits, which could then affect your fertility.

Moreover, your ideal weight for running that 5k or fitting into your skinny jeans may not be the weight most conducive to conceiving. “You don’t have to be a size 6 to have a baby,” says lead study researcher and ob-gyn Abbey Berenson, MD. “This isn’t about what looks good on a runway. It’s about making your body healthy enough to carry a child.” The sweet spot for many women translates to the normal BMI range (18.5 to 24.9), which is associated with optimal reproductive function. Research shows that 12 percent of infertility cases may result from being under that range and 25 percent from being over it. The two extremes tax the body in ways that disturb hormone production and ovulation, Dr. Brzyski says.

Even so, BMI is not always the best way to assess how weight will affect reproductive function. The measurement is based on height and weight and doesn’t distinguish between fat and muscle — and fit women have a lot of lean muscle mass. William Schoolcraft, MD, founder and medical director of the Colorado Center for Reproductive Medicine in Denver and author of If at First You Don’t Conceive, often sends his patients to an exercise physiologist to measure their body fat percentage (through skinfold-caliper or buoyancy testing) instead.

How your weight affects your fertility:

Though disrupted cycles and missed periods are commonly associated with elite athletes, Jamie Grifo, MD, PhD, director of the NYU Fertility Center in New York City, also sees his share of weekend warriors who overdo it. “I tell them to scale back,” he says. “You want your body to be a fertility-promoting environment.” More than an hour of vigorous exercise a day can lead to a decrease in the production of the hormones that stimulate ovary function, causing ovaries to become underactive and stop producing eggs and estrogen, in some women. The risk increases with exercise duration and intensity. What’s more, Dr. Schoolcraft says, intense exercise sessions cause the body to break down the proteins in muscles, producing ammonia, a pregnancy-inhibiting chemical.

It seems counter-intuitive that something that makes you feel good and has been proved to protect your body against myriad diseases and health problems can actually be bad for your fertility. Here’s what happens: “Intense exercise lowers progesterone and throws off your hormone levels,” says Sami David, MD, a reproductive endocrinologist in New York City and coauthor of Making Babies: A Proven 3-Month Program for Maximum Fertility. “Endorphins can suppress your FSH and LH, the hormones in your pituitary gland responsible for producing eggs, and the ovarian hormones estradiol and progesterone, making it harder for you to get pregnant or more likely to miscarry without knowing it.” The bottom line: “The extremes of exercise — too much or too little — are never good,” Dr. Grifo says. “You need to find a balance between the two; that’s when your body functions optimally.”

Advice to boost your fertility:

The default stance is that normal-weight women should work out for 30 minutes of moderate-intensity activity (you break a sweat and are winded but can still speak in short phrases) five days a week. Under- or overweight women should seek evaluation from a certified fitness professional, like an exercise physiologist or trainer, to tailor a program based on their energy input and output, Dr. Dugan says.

Here are some tips depending on your current weight:

If you are normal weight:

There is no need to give up your regular runs or, say, Zumba classes. Just keep your workouts to an hour or less a day. If your cycle is irregular or you haven’t conceived after a few months, cut back further on exercise. Also, this isn’t the time to train for your first competitive event or start a rigorous gym class. “If you make a dramatic increase in your exercise level, even if BMI or body fat percentage stays the same, the stress can have a negative effect on reproductive hormone production and fertility,” Dr. Brzyski says.

If you’re underweight:

Aim for 2,400 to 3,500 calories a day to gain the weight that will get you into the normal BMI range, or body fat above 12 percent. If you’re exercising five or more days a week, consider cutting back to three. Alice Domar, PhD, executive director at the Domar Center for Mind/Body Health at Boston IVF, says that yoga appeals to many women in this category: “It keeps them fit and toned without the potential adverse impact of vigorous exercise.”

If you’re overweight:

Trim calories and gradually up your exercise to reach a fertility-friendly BMI. Aim for 60 minutes of cardio five days a week, and strength-train for 30 minutes three times a week. Even so, “you can work out too hard even if you’re overweight,” Dr. David cautions. “Build up your tolerance slowly.”