Does breastfeeding REALLY make you lose weight?

Of all the touted benefits of breastfeeding, the idea that I would effortlessly lose all of the baby weight was a major motivator for me. Unfortunately, in my case, it turned out to be false. I breastfed my eldest child for a year and a half, and lost most of my pregnancy weight within the first month, but then I started regaining it. My experience has been roughly the same with my second child, who’s still nursing at almost one year old. The pervasive belief that women can easily “bounce back” right away thanks to nursing just isn’t the reality for all women.

Technically, you do burn calories when you breastfeed: 300 to 500 per day. But that doesn’t necessarily mean you’ll lose weight—it’s more complex than that. Calorie counts don’t account for the diversity of body types among women, and sleep, stress, eating habits, physical activity, hormone changes, total pregnancy weight gain and the number of previous pregnancies will all determine whether you return to your pre-baby weight.

Yoni Freedhoff, a family physician and author of The Diet Fix, says the number of calories burned during breastfeeding may not be significant enough to offset the stress, lack of sleep and change in diet many women experience after giving birth.

Lauren Olofsson, a registered dietitian and lactation consultant, agrees. She says stress—brought on by the sleep depri­va­tion and 24/7 work of caring for a newborn—increases cortisol levels, and high cortisol levels have been associated with weight gain.

Olofsson has seen a wide range of experiences among her breastfeeding clients: While some women have to eat more in order not to lose too much weight, others hold on to extra weight until they stop nursing. And then some women, like me, initially lose weight but find themselves gaining it all back a few months in.

There’s also some evidence that prolactin, the hormone responsible for the production of breastmilk, not only slows down the body’s metabolism of fat but may also act as an appetite stimulant. In a 2004 study in The American Journal of Clinical Nutrition, researchers actually found that lactating women retained more weight than non-lactating women, presumably “due to the influence of prolactin on appetite stimulation.”

Some women may mistakenly treat breastfeeding like a no-effort diet. A 2016 study conducted in Sweden found that misconceptions regarding breastfeeding actually led some women to eat more because they assumed the pounds would melt off. “This reliance on breastfeeding for automatic weight loss was perceived as reinforced by friends, media and medical staff, and gave women a false promise of easy postpartum weight loss that lowered their motivation to limit their weight gain during pregnancy or eat healthy postpartum,” the researchers wrote. Plus, many new parents simply don’t have the time, child care help or energy to be diligent about diet and exercise—they’re in survival mode. Plus, when you’re sleep-deprived, an extra caffeine break—and a sweet snack to go with it—is extremely hard to resist. (In fact, it feels like a sanity-saving reward for successfully getting out of the house with your baby!)

Even following a rigorous professional-athlete workout routine and strict diet isn’t a guarantee of weight loss while nursing. During Wimbledon last summer, Serena Williams said, “You hear that when you breastfeed you lose weight and you’re so thin... For my body, it didn’t work, no matter how much I worked out.” But when she weaned her daughter, she quickly lost 10 pounds.

There have been numerous studies on breastfeeding and weight change, but the results are inconclusive. One 2003 study found a mother’s body mass index was a greater predictor for whether she would lose weight while breastfeeding; thin women tended to lose weight easily, while overweight women tended to retain weight. A widely cited 2014 review of research on the subject, however, found no significant relationship between the two; in fact, it noted that other factors such as age, weight gained during pregnancy, and duration and intensity of nursing (exclusive versus partial) also need to be considered in future studies. The researchers concluded: “The findings undoubtedly challenge the common belief portrayed across scientific literature that breastfeeding promotes weight loss.”

I wish I had been more accepting of my body—and the fact that women’s bodies change after having a baby—when I was a new mom. This second time around, I’m trying not to feel bad about my larger postpartum belly. While I continue to be a strong advocate for breastfeeding (I love the benefits for my baby and the bonding time it provides), I want women to know they should not be making this choice solely to cancel out calories.