Breastfeeding melts off the baby weight, right? Or so we are told. Breastfeeding leads to an “earlier return to prepregnancy weight,” according to the American Academy of Pediatrics (AAP).
This is because “breastfeeding burns extra calories, so it can help you lose pregnancy weight faster,” as many popular websites, like WebMd claim.
Sounds pretty clear cut, right?
So when I failed to lose weight while breastfeeding my first child, I was shocked. Weren’t those pregnancy pounds supposed to practically fall off? Why were my pre-pregnancy jeans still relegated to the back of my closet?
Breastfeeding an infant does burn an average of 480 calories a day. So why wasn’t I losing more weight?
But like so many other alleged benefits of breastfeeding, breastfeeding-aided weight loss turns out to be vastly overblown.
In other words, my experience was completely normal. For most well-nourished women, long-term breastfeeding results in only a trivial amount of extra weight loss by 6 months postpartum, usually only of 1-2 lbs.
“In most reports, rates of weight loss did not differ between lactating and nonlactating women.” states a 1998 review of the research on postpartum weight loss.
“The effect of breastfeeding in mothers on return-to-pre-pregnancy weight was negligible, and the effect of breastfeeding on postpartum weight loss was unclear,” concludes another large 2007 review.
Large research reviews all find that breastfeeding does lead to greater weight loss at 6 months after birth, but that the amount lost is so tiny as to be trivial: Breastfeeding mothers shed an extra 1-2 lbs on average–provided they breastfed for at least 6 months. Breastfeeding during the first 3 months after giving birth has no effect on weight.
(According to a 2015 review, randomized controlled trials put the added weight loss for breastfeeding mothers at an average of about 1 lb. Cohort studies report a greater amount, of about 2.5 lbs. The true benefit is thus probably closer to an average of 1 lb than of 2.5 lbs.)
In short, while there may be lots of good reasons to breastfeed, weight loss does not seem to be one of them.
Why Doesn’t Breastfeeding Lead to Greater Weight Loss?
Breastfeeding sure seems like it ought to lead to significant weight loss. Breastfeeding, after all, does require calories. Lots of them. Women burn between 400-560 extra calories a day breastfeeding during the first 6 months after giving birth, the amount burned by an hour of running.
So why aren’t breastfeeding women shedding their baby weight?
Unfortunately, when it comes to taking off those extra pregnancy pounds, your biology is working against you.
In food-rich environments, breastfeeding women make up for the extra calories burned breastfeeding not from fat reserves, but by eating more and moving less.
Breastfeeding makes you hungry. Prolactin, the major hormone regulating breast milk production, is released each time you nurse; it is a potent stimulator of appetite.
Prolactin may explain why breastfeeding frequency is inversely related to weight loss–the more often women breastfeed, the less weight they tend to lose.
During the first 3 months of breastfeeding, when feedings are most frequent, breastfeeding moms lose weight at the same rate as formula-feeding moms. But between 3 to 6 months, when milk production remains high but feedings are spaced further out, breastfeeding moms lose a little more weight–an additional 1-2 lbs, on average–than formula-feeding moms,
In the past, prolactin’s stimulatory effect on appetite was adaptive. When living in an environment with a scarce or unpredictable supply of food, you need to save those precious fat reserves laid down during pregnancy for times of shortage.
But these days, the boost in appetite is arguably maladaptive, at least in developed countries, where food is plentiful and in constant supply. The shortage never comes, so women tend to hold onto their pregnancy fat reserves indefinitely.
Prolactin is just one piece of the weight loss problem. Lack of sleep is also a likely culprit.
Babies who are formula-fed are far more likely than breastfed babies to sleep through the night by 3-4 months of age, whereas breastfed babies tend to wake up to nurse in the middle of the night until 9-10 months of age.
Inadequate, broken sleep, such as that of new parents, wreaks havoc on the appetite. The body shifts into crisis mode, trying to conserve energy for what it assumes must be hard times. Energy levels tank. The hormones regulating appetite downshift into starvation mode: Levels of leptin, a hormone dampening appetite, drop, while levels of ghrelin, a hormone stimulating appetite, rise. Poor quality sleep increases activity in brain areas sensitive to rewarding, highly desirable foods, making it harder to resist high-calorie food.
Biology is not the only force working against weight loss while breastfeeding. For many women, breastfeeding, especially exclusive breastfeeding, poses serious logistical challenges to getting exercise. Breastfeeding on demand sucks away a tremendous amount of time. Who can fit in a workout when they are nursing every 2 to 3 hours for half an hour at a time?
Exclusive breastfeeding also makes it hard for other people to give you a break, so you can go to the gym or out for a walk.
This was certainly true for me. Both of my children refused, and I mean refused, to take a bottle. By 2 months of age, the mere sight of a bottle would send my son into hysterics. During the first 6 months after I gave birth, I could sneak away from him for at most an hour at a time.
The Bottom Line
Despite burning a considerable number of calories, breastfeeding has a negligible effect on body fat and total body weight for most well-nourished women.
The medical establishment, as well as many researchers, seems reluctant to admit this. For example, many of the research articles cited in this post have titles that suggest breastfeeding has a major impact on weight loss. Dig into their actual findings, though, and you find a different story: the differences in weight loss between breastfeeding and formula-feeding mothers are almost always small, and often vanish altogether when other factors, like age, gestational weight gain, and prepregnancy weight are taken into account.
Some of this reluctance may be because science can never “prove” a null result. It is always possible that the lack of an effect is due to poor study design, or poor measurement, or some other form of bias. A series of better-designed studies could find that breastfeeding leads to significant weight loss.
Still, when the vast majority of the evidence does not support the idea that breastfeeding helps women lose their pregnancy weight, major medical organizations like the AAP have no business stating otherwise.
The emphasis on breastfeeding for weight loss almost feels like a bait-and-switch. Because in fact, when it comes to holding onto extra pregnancy pounds, the biggest factor is not breastfeeding, but how much weight you gained during pregnancy.
What about you? Did breastfeeding help you lose your pregnancy weight?
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