Will Exercising Reduce My Breast Milk Supply?

You're ready to get back to your pre-pregnancy exercise routine, but will it harm your ability to breastfeed your baby?

Exercise doesn't have to breast milk impact supply. Shutterstock/Ken Tackett
For new moms, returning to an exercise routine can be a saving grace: It's a chance to reconnect with your body and have some much-needed time to yourself. If you're trying to breastfeed your new addition, however, you might worry about the ways exercise will affect your supply. Establishing a milk supply large enough to feed your baby is essential in the early days, and it can set you up for a successful breastfeeding relationship that can last as long as you want it to.

So, will burning calories in the gym change your body's ability to make breast milk? We talked to the experts to find out.

There's no evidence that working out hurts your breast milk supply.

While there hasn't been too much scientific study of the effect of exercise on breast milk supply, the research that has been done has good news for moms: It seems to be completely OK to hit the gym as soon as your doctor clears you for exercise. One review of scientific studies concluded, "It appears that mothers can exercise and breastfeed without detriment to the growth of their infants."

Wendy Wisner, an International Board Certified Lactation Consultant from New York City, agrees that exercise should not affect supply. "I have never seen it be an issue in the hundreds of mothers I have worked with," she says. "There is no reason to be worried about working out decreasing your supply."

In fact, exercise may even help breastfeeding.

Breastfeeding success and milk production can be affected by stress, so if you're leaving the gym feeling refreshed and renewed, exercise could actually have a positive effect on your supply. "Some mothers find that exercise relaxes them, and helps them 'let-down' more easily," Wisner says, referring to the feeling many moms get when their milk begins to flow during a nursing session.

There may be another, somewhat stranger reason that exercise benefits supply: nipple stimulation. When your breasts are moving during exercise—particularly cardio—you may stimulate your nipples and increase the hormones that tell your body to create milk, says Sara Pelfrey, a postnatal exercise specialist and owner of Moms2BFit, a training service for moms in Charlotte, North Carolina. "Any nipple stipulation increases supply, and running and things like that do the same thing," she says.

But be smart about workout wear and exercise choices while nursing.

There are, however, some things for nursing moms to think about before hiting the gym. First, it's important to have the right equipment. "The right sports bra is essential," Pelfrey says. "You still need a good level of support, but something that is adjustable." A sports bra that is too tight can compress your breasts, putting you at increased risk for blocked ducts or mastitis.

Wisner adds that certain exercises can also increase your chances of getting blocked ducts. "The only warning I would give would be with weight lifting or weight-bearing exercises—like push-ups or pull-ups—because sometimes these can cause plugged milk ducts," she says.

Don't forget to fuel up.

Unsurprisingly, feeding a growing baby is no small job, and breastfeeding burns extra calories. The Mayo Clinic recommends that breastfeeding moms eat an additional 400 to 500 calories per day to keep their energy up. If you're hitting the gym as well, you may want to eat even more than that.

"If you are working out strenuously, you will probably find yourself extra hungry," Wisner says. "Breastfeeding usually burns about 500 calories anyway, and if you are burning more, you will need to refuel." Although many moms want to lose the baby weight quickly, it's important to remember that calorie restrictions—especially if you're working out—aren't a good idea while breastfeeding.

A weight loss of up to a pound a week is healthy, Pelfrey says, but don't expect more than that. Instead, use this postpartum time to focus on building strength, rather than worrying about the pounds. Restricting calories below 1,500 per day has been shown to negatively impact supply, Wisner adds, as has losing weight too quickly. Nursing moms should be sure to eat lots of nutrient-rich foods to nourish both themselves and their babies' breast milk.

And don't forget to drink extra water while you're at it: "A breastfeeding mother often feels more thirsty while breastfeeding," Wisner says. "There is no particular amount she needs to drink to keep her supply up; she should drink to satiate her thirst. Most mothers will find that working out makes them extra thirsty for sure."

Focus on how you're feeling.

New moms who are returning to exercise might worry about their breast milk supply, but really they should be focused on their own reactions to exercise. Listen closely to your body to determine what level of exercise is right for you during the postpartum period. "You may feel wiped out by early motherhood and all of its demands, so take it slow for your own sake," Wisner says.

Pelfrey agrees: "Exercise at a moderate level that makes you feel more energized not completely wiped out."

If your supply does dip, consider all the possible causes.

Pelfrey points out that many new moms start working out regularly at the same time that other changes are happening, most notably returning to work. If you do notice your supply dropping, evaluate whether exercise is to blame, or if other changes, like incorporating pumping and nursing less, could be impacting your breast milk production.

If you do notice a change, a lactation consultant can often help you reestablish supply while also keeping your fitness and lifestyle goals in mind.