Like so many new moms, I was told ad nauseam that breastfeeding melts off baby weight. And not just by random strangers. The American Academy of Pediatrics (AAP). states that breastfeeding leads to an “earlier return to prepregnancy weight”.
Breastfeeding supposedly helps you lose weight, because, as many popular websites, like WebMd claim, “breastfeeding burns extra calories, so it can help you lose pregnancy weight faster.”
Sounds pretty convincing, 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?
By exclusively breastfeeding, I was burning an average of 480 calories a day, but the pregnancy pounds were still clinging to my waist and hips.
So, naturally, I turned to the research, and learned that, like so many other widely alleged benefits of breastfeeding, breastfeeding-aided weight loss is vastly overblown.
My experience was not weird, but completely normal. For most well-nourished women, long-term breastfeeding results in only a trivial amount of extra weight loss by 6 months postpartum, of around 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?
Baker JL, Gamborg M, Heitmann BL, Lissner L, Sørensen TI, Rasmussen KM. Breastfeeding reduces postpartum weight retention. Am J Clin Nutr. 2008 Dec;88(6):1543-51. doi: 10.3945/ajcn.2008.26379.
Butte NF, Wong WW, Hopkinson JM. Energy requirements of lactating women derived from doubly labeled water and milk energy output. J Nutr 2001;131:53–8.
Butte NF, Hopkinson JM. Body composition changes during lactation are highly variable among women. J Nutr. 1998 Feb;128(2 Suppl):381S-385S.
Copinschi G, Leproult R, Spiegel K. The important role of sleep in metabolism. Front Horm Res. 2014;42:59-72. doi: 10.1159/000358858.
Dewey KG, Heinig MJ, Nommsen LA. Maternal weight-loss patterns during prolonged lactation. Am J Clin Nutr. 1993 Aug;58(2):162-6.
Dewey KG, Heinig MI. Nommsen LA, Lonnerdal B. Maternal versus infant factors related to breast milk intake and residual milk volume: the DARLING study. Pediatrics 1991:87:829-37.
Goldberg G. R., Prentice A. M.,Coward W. A.,Davies H. L., Murgatroyd P. R., Sawyer M. B., Ashford J., Black A. E. (1991) Longitudinal assessment of the components of energy balance in well-nourished lactating women. Am. J. Clin. Nutr.54:788–798.
Gore SA, Brown DM, West DS. The role of postpartum weight retention in obesity among women: a review of the evidence. Ann Behav Med. 2003 Oct;26(2):149-59.
Gross BA, Eastman Cl. Prolactin and the return of ovulation in breastfeeding women. I Biosoc Sci l985;9(suppl):25-42. 14.
He X, Zhu M, Hu C, Tao X, Li Y, Wang Q, Liu Y. Breast-feeding and postpartum weight retention: a systematic review and meta-analysis. Public Health Nutr. 2015 Apr 21:1-9.
Howie PW, McNeilly AS. Effect of breast-feeding patterns on human birth intervals. I Reprod Fertil 1982:65:545-57.
Ip S, Chung M, Raman G, Chew P, Magula N, DeVine D, Trikalinos T, Lau J. Breastfeeding and maternal and infant health outcomes in developed countries. Evid Rep Technol Assess (Full Rep). 2007 Apr;(153):1-186.
Nehring I, Schmoll S, Beyerlein A, Hauner H, von Kries R. Gestational weight gain and long-term postpartum weight retention: a meta-analysis. Am J Clin Nutr. 2011 Nov;94(5):1225-31. doi: 10.3945/ajcn.111.015289.
Neville CE, McKinley MC, Holmes VA, Spence D, Woodside JV. The relationship between breastfeeding and postpartum weight change–a systematic review and critical evaluation. Int J Obes (Lond). 2014 Apr;38(4):577-90. doi: 10.1038/ijo.2013.132.
Oken E, Patel R, Guthrie LB, et al. Effects of an intervention to promote breastfeeding on maternal adiposity and blood pressure at 11.5 y postpartum: results from the Promotion of Breastfeeding Intervention Trial, a cluster-randomized controlled trial. The American Journal of Clinical Nutrition. 2013;98(4):1048-1056. doi:10.3945/ajcn.113.065300.
Østbye T, Peterson BL, Krause KM, Swamy GK, Lovelady CA. Predictors of postpartum weight change among overweight and obese women: results from the Active Mothers Postpartum study. J Womens Health (Larchmt). 2012 Feb;21(2):215-22. doi: 10.1089/jwh.2011.2947.
Spiegel K, Knutson K, Leproult R, Tasali E, Van Cauter E. Sleep loss: a novel risk factor for insulin resistance and Type 2 diabetes. J Appl Physiol (1985). 2005 Nov;99(5):2008-19.
Spiegel K, Tasali E, Penev P, Van Cauter E. Brief communication: Sleep curtailment in healthy young men is associated with decreased leptin levels, elevated ghrelin levels, and increased hunger and appetite. Ann Intern Med. 2004 Dec 7;141(11):846-50.