One thing that many new parents struggle with is losing the baby weight while they are breastfeeding. How many calories does breastfeeding burn, exactly? Here’s how you can figure that out.
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When I was pregnant with my son, I gained 55 pounds, which is 20-30 pounds over the recommended weight gain.
After he was born, I didn’t feel happy with my body and wanted to lose some of that baby weight. During the first month postpartum, I lost the 10ish pounds that constituted the baby, placenta, and amniotic fluid, plus another 20 or so pounds of water.
That left me with about 25 pounds to lose, and I wanted to get started – but I wasn’t sure exactly how breastfeeding would impact how much I should be eating. Here’s the info I came up with after hours of searching for evidence-based answers.
How many calories are in breast milk?
Before we talk about how many extra calories you burn, let’s discuss how many calories are in the breast milk that you produce.
This matters because the energy that goes into breast milk isn’t spontaneously created in your breasts – it has to come from the food that you eat or from your fat stores.
Each ounce of breast milk has about 20 calories; for those using the metric system, 10 mls of breast milk has about 6.8 calories.
If you are exclusively pumping, here is one area where you actually have an advantage!
When you are pumping and able to accurately measure your milk output, you know exactly how many ounces (or milliliters) of milk you are producing.
Therefore, it’s very easy to calculate how many calories in the breast milk you are producing:
(# of oz * 20) = Total Calories in Breast Milk
As an example, let’s say that you pump 20 ounces of breast milk per day.
20 oz * 20 = 400 calories
Again, this comes from the food you eat or your fat stores.
So how many extra calories do you burn when you’re making milk?
Many breastfeeding resources will tell you that you burn an extra 300-500 calories while breastfeeding.
The thing is, “breastfeeding” can mean a lot of things, and the calorie burn for all of them is different. For example, you’ll produce a much different amount of milk – and thus burn a different amount of calories – if you are exclusively breastfeeding twins than if you are combo nursing and formula feeding one child.
At one point with my son, I was pumping 50 ounces per day, which is 1,000 calories of milk produced. That is an awful lot more than that 300-500, which would explain why I was so freaking hungry.
Want to get even more precise?
Multiplying by the 20-22 calories in the milk does not take into account the energy that your body requires for the internal process of making your breast milk.
The total calories that you burn by breastfeeding are the calories in the milk plus the energy burned to producing the milk.
The production efficiency for breast milk production is 80% of the energy in the milk itself. This means that of all the energy required to produce breastmilk, 80% of it ends up in the milk, while 20% is used by your body to make the milk.
Breastfeeding calorie burn calculation formula
We can modify the formula from above to take the production efficiency into account in the below breastfeeding calorie burn calculation formula.
(# of oz * 20)/0.8 = Total Breastfeeding Calories Burned
Let’s go though an example.
Say you pump 20 oz over the course of a day:
(20 oz * 20 calories)/0.8 = 500 total breastfeeding calories
First, you would multiply the 20 oz by the 20 calories that is in the milk, which would give you the 400 calories that are in the breast milk.
Then, you would divide that by .8 (the production efficiency), which gives you 500 – the total calories burned by breastfeeding, including the milk you make (400 calories) AND the energy you burned making the milk (100 additional calories).
Another way to think about the production efficiency thing – which can be confusing – is that, in this example, your body devoted 500 calories to making breast milk. Of that, 400 (80%) made it into the milk, while 100 (20%) was used by your body.
Here’s the metric system version of the breastfeeding calorie burn formula:
(# of ml * .68)/0.8 = Total Breastfeeding Calories
How can you tell how much breast milk you’re producing when you’re nursing?
Now, if you’re not an exclusive pumper and want to determine how much milk you’re making, you have a few options:
- Take one day where you weigh your baby before and after every feeding using a scale like this. Subtract the before weight from the after weight to determine how much your baby ate. At the end of the day, total the baby’s intake from all the feedings and plug it into the above formula!
- Pump and bottle feed your baby for 24 hours and then multiply the number of ounces you pump by 20.
Does pumping burn the same amount of calories as nursing?
If you produce the same amount of breast milk pumping as you do nursing, then yes.
Say you’re nursing your baby and she nurses like a champ, but your body doesn’t respond well to the pump and you don’t pump much milk when you’re at work. You would burn fewer calories at those pumping sessions than you would if you were nursing then, because you are producing less milk.
On the other hand, say you’re exclusively pumping and have a large oversupply. You’re burning MORE calories that you would if you if you were nursing, because you’re producing way more milk than your baby would otherwise eat.
One last thought
Having a baby is a big deal for your body, and you are beautiful just the way you are.
I wrote this post not to encourage new parents to lose the baby weight, but because if you want to understand how breastfeeding and calories work, you deserve better information than a vague, one-size-fits-all number.
Hopefully this helps answer any questions you have about how many extra calories you burn while breastfeeding! Let me know if you have any questions in the comments.
Want more information about losing weight while breastfeeding? You can read about exercising and breastfeeding here and my experience with losing weight while breastfeeding here.
References- Bonyata, Kelly, IBCLC. “Do breastfeeding mothers need extra calories or fluids?” https://kellymom.com/nutrition/mothers-diet/mom-calories-fluids/
- Lovelady, Cheryl A., et. al. “The Effect of Weight Loss in Overweight, Lactating Women on the Growth of Their Infants.” https://www.nejm.org/doi/full/10.1056/NEJM200002173420701#t=articleBackground
- O’Connor, Anahad. “How Sleep Loss Adds to Weight Gain” https://well.blogs.nytimes.com/2013/08/06/how-sleep-loss-adds-to-weight-gain/?_php=true&_type=blogs&_r=0
- Ruani, Alejanda. “The No. 1 Lazy-Proof Strategy to Lose Weight” https://www.huffingtonpost.com/alejandra-ruani-/sleep-weight-loss_b_4755013.html
Oh my goodness, thank you so much. I too was tired of hearing the “about 500 calories”. I am so grateful for the formula. All of the craziness I have been experiencing now makes sense. At point I was pump 24 to 31 oz per day in addition to nursing 4 to 5 times. I felt like a zombie since this was after going back to work. I just started using MFP this week in and effort to lose the last 12 pounds. But will not stress if there isn’t alot of progress until after my son wants. Thanks a million for doing all that research. Much appreciated.
Amanda, help! I feel alone because I don’t seem to fall into either of the two categories listed. Just had my first baby boy at age 37, gained a whopping 70 pounds with him, ugh! I didn’t have any health problems or complications, I just feel like my body is super-sensitive to hormone changes. Within 6 weeks of being post-partum I dropped about 30 lbs but unfortunately I am now 14 weeks and haven’t been success in so much as a pound since. I pump and exclusively feed, and I would say I pump 12-16 oz. as well as feed when I am home from work (possibly 6-8 additional oz.). I am tracking what I eat (around 1700 cals per day) and trying to walk and sleep as baby permits lol. What am I doing wrong?! Are there any other considerations I am not thinking of that would impact my ability to lose this last 40, YIKES! Any other mamas experiencing this?
Hi Alynn! I think this is totally normal and LOTS of moms experience this. (That doesn’t mean that it isn’t super frustrating.) It sounds like you are doing everything right. I think you might be one of those women that just really struggles to lose weight when breastfeeding? I think it will be easier when you’ve weaned. I’m so sorry you’re dealing with this. You are doing a great job!
I know this post is a few months old, but I just wanted to leave a little solidarity message. I nursed and pumped with my son 5 years ago (i was 32). I’d gained between 50 and 60 pounds with my pregnancy, dropped about 30 of those pounds in my first 6 weeks, and didn’t budge another pound until after I’d weaned. I’d also had hormone challenges, and ended up getting help from my DO to balance out my estrogen and progesterone, and supporting a low functioning thyroid.
I’m now 15 weeks postpartum (age 37), and following almost the exact same pattern. I gained between 50 and 60 pounds, dropped exactly 30 pounds in the first 6 weeks, and haven’t budget an ounce since. I’m exclusively pumping this time around (averaging about 40-50 oz a day). It’s also the holidays and the weather is terrible, so eating well and getting a walk in just aren’t happening.
I’ve sort of just accepted this is how my body does postpartum, bought some bigger pants, and am anxious for spring when I can breathe some fresh air and walk a bit. Hoping other mommas have a bit of hope that the weight will eventually come off, it just may not come off while breastfeeding.
Thank you for all that information Amanda. I am wondering if the quality of the milk could change if we diet while breastfeeding. Also- how can you pump so much milk? I work in millilitres and was amazed at the amounts you are able to pump when I calculated them. I am breastfeeding my 5 weeks old baby and he is constantly feeding. I am also giving him top-ups so I pump my breast milk and give him to him. Midwife asked me to feed him with both breast and then pump 10min. I used to pump for longer with my electric pump ( single ) and still can’t achieve a larger amount. It is better than with the manual pump, I tried it with the manual pump with my daughter and it was driving me mad! She breastfed only and was breastfeeding for two years so the milk is there … I am excited to hear how you can make it work… thanks
Hi Gema! Thank you so much! I wouldn’t be tooooo worried – moms in famine conditions make perfect breastmilk.
I wouldn’t expect you to pump that much (or anywhere near it) if you are nursing first! I was only pumping, but your baby is getting most of your milk through nursing. 🙂
Thanks for this post. It answered so many questions for me!!
Thank you so much for this article! I’m a huge overproducer as well / making 100 Oz per day!! Then I want to eat all the sweets! I have been beating myself up because of my lack of motivation to work out but this makes me feel better. I am hungry all the time!!! Time to buy some healthy snacks stop with the cereal and sweets!
I’m an overproducer, also! I freeze about 50-60 oz/day, plus take 24 oz of fresh milk to the sitter for my picky eater/workday, plus feed him on demand when I’m with him in the evening (I’m guessing he gets another 15-30 with me/day). On the low side of those numbers, my calorie intake would need to be 2225 extra! That is why I eat all day long! So hungry!!! Thanks for the info Amanda!
How many calories should you be eating in the first place to want to lose weight before adding these extra on to them? And do you add more calories if you exercise?
Thank you so much for this post! I can’t seem to ever eat enough for my body to let the baby weight go, it’s been so frustrating.
Hi Emmy! I can’t answer the first one – it depends on your current weight and height and body frame and other stuff. Maybe plug your stats into an app like MyFitnessPal and see what it suggests, then add the breastfeeding calories?
I always did add more calories for exercise.
I’m sorry I’m lost at the math. You are saying to make say an oz, I need 80% of the calories 1 oz is worth (I.e. 80% of 20 calories). So if I make 20 oz, how is the calorie needed for it 500? Shouldn’t it be 320? Could you let me know what am I missing?
Sure. So say you make 20oz.
First you have the calories IN the breastmilk: 20oz * 20 calories = 400 extra calories
PLUS you have the energy needed to make the milk. You can get this number by dividing by .8. 400 calories divided by .8 is 500, meaning your body uses 100 calories to make that 400 calories of breastmilk, therefore breastfeeding would require 500 extra calories.
(400 MULTIPLIED by .8 is 320, which I think is the confusion.)
So although I think this article is awesome and super helpful and exactly what I was looking for(thank you for doing all the work that I was trying to do, but felt overwhelmed with!), I have to agree with SSR. If what you’re saying is that the number of calories burned to produce the milk is 80% or the output, then you would actually multiply. If your output is 400 calories, 100 calories is only 24% of that. Half, which is 50%, is 200 so at 80% you be almost doubling your calories burned. So to do the math you would have to take your ounces produced and multiply by 20 and then take that result and either multiply by .8 or divide by 8. So 20oz*20 calories=400 extra calories then multiply by .8= 320 calories. 320/400=.8 which is 80%
Hi there! So for this:
If what you’re saying is that the number of calories burned to produce the milk is 80% or the output,
That’s not what I’m saying, and I’m so sorry if it’s confusing. the total calories burn is the FULL output, plus MORE to make the milk. To calculate that, you can divide by .8. I used to have a more intuitive but longer formula, but replaced it with this one because it was simpler to do. Sorry about that!
So its 400 calories (full output) plus 100 calories to make the milk.
Thank you so much for this article!! I produce like 80 to 90 fl ounces per day…I am hungry like all the time. I also drink a ton of water all the time. It’s crazy I burn that much just making milk…but I figure it was a lot because I probably eat 3000 calories per day to maintain my weight and if I don’t I lose weight. I know once I am done producing I will lose the last 10 lbs.
I have a 9 month old EBF Baby pre baby i was weighing 120 now im weighing 180 its hard dealing with the different weigh and also battling ppd & sleep deprivation at the same time since he still wakes up to nurse every 2 hours during the night , then in the day i find it so hard to find time to even try to workout or the energy to 🙁 and not to mention i eat so much because im starving always!
Oh my god, THANK YOU! I’m a data geek and I just wanted the pure numbers. I’ve been beating myself up for not being able to stick to a diet and yet when I factor in how much I’m actually burning, I’m doing just fine. (And I’ve seen it reflected on the scale .. how dumb is that to still beat up on myself? haha). Now I can meal plan way more effectively.
So, am I right that instead of using that 2-step formula to calculate the calorie cost to make milk, could one just do the figure once to see that it costs 25 calories to make an ounce – and so take that and go 25x(OuncesOfMilk)=(CaloriesSpent) ? Much simpler math for this tired mom lol…
I think that will work – good call!!! 🙂
I love the math. Thank you so much. I’m an over producer does this mean I can’t lose baby weight? I burn 1500 calories just from pumping milk according to the math. If I’m 5’7 and 255 pounds, mfp says 1900 calories to lose weight (at a 20% deficit) I’ve done this, but I am not losing any weight. Do I add 1500 calories to the 1900? That’s 3400 calories! Won’t I be gaining weight at that point or what? I’m a bit lost on this and desperately looking for the weight loss. Thank you!
Hi Sarah! How old is your baby? Have you gotten your period back at all? Some women seem to really struggle to lose weight when they are breastfeeding regardless of what they do. So frustrating!
I love you! Seriously, I’ve been wanting to know all this information and haven’t known how to research it on my own, so thank you! I don’t pump, so I’ll have to see how much milk I’m producing in one of those other methods, but this is incredible! Considering my daughter is exclusively breastfed and by 2 months old she weighed over 14 pounds, I think I’m producing quite a bit of milk! I’ve been working hard to lose weight but I’ve also been worried about my milk supply. This information you’ve kindly researched and shared for the rest of us mamas is everything I needed! Thank you!
Than you so much for all that great SPECIFIC info! I dont pumo but my 5 month old feeds like crazy and I work out 3 days a week, an hour per session, cardio and strength training. I’m ravenous all the time and I’d often wonder why no websites mention the increase in calories burnt as your baby gets bigger and needs more milk.
TMI, I was wondering if theres any chance if my boobs getting smaller once I’ve weaned? I’m a size D now and I cant wear shirt comfortably anymore. Is there a chance that losing more weight would help me go down a cup or two? Thanks so much xoxo
Hi Ren! Mine totally did when I weaned (… too much, ha!), so I think there’s a good chance!
It’s like you found out what I couldn’t pinpoint that I really wanted to know! Thank you for how specific this post was. I appreciate the research that went into it! The vagueness also bothers me. This gives me info I can use.