When I decided to start trying to lose weight after I had my first baby, I was exclusively pumping for my son and was concerned that trying to lose weight would impact my milk supply. I also wasn’t sure how many extra calories I needed for breastfeeding. After doing some research, I figured out a formula to calculate the exact number of calories I was burning by pumping breast milk.
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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. I think part of the reason behind this was that I was really hungry all of the time, part of it was water, and a lot of it was due to “eating my feelings.”
I had had 3 miscarriages before my first child was born – one of them after the first trimester – so I had a lot of anxiety about my little one that I dealt with in the form of ice cream.
So when my son was born, I felt gross and wanted to lose the baby weight as quickly as possible. 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 do it as quickly as possible – but I wasn’t sure exactly what the “rules” were. Here’s the info I came up with after hours upon hours of searching the internet for evidence-based answers.
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. When it comes to weight loss, vagueness like this drives me crazy. Personally, I do much better with a very specific understanding of what I am burning and, therefore, how much I should be eating.
A vague “300-500” calories when I’m starving is really frustrating, because I don’t know if I can really have that extra 200 calories and still be successful in losing weight.
Here is one area where exclusively pumping actually has its advantages! Because you are pumping and therefore able to easily and 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 of your caloric output from milk – each ounce of breast milk has 20 calories (10 mls has 6.8 calories), and this energy isn’t spontaneously created in your boobs. So, if you pump 20 ounces per day, you are using 400 additional calories to feed your baby. If you are pumping 30 ounces, then 600 calories, and so on.
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 and also why the vagueness made me insane.
So an easy way to determine a basic estimate of how many extra calories you are burning due to breastfeeding is take your total pumping output for the day and multiply it by 20.
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, multiply it by 20, and you have a good estimate!
- Pump and bottle feed your baby for 24 hours and then multiply the number of ounces you pump by 20.
Want to get even more precise?
Multiplying by 20 does not take into account the energy that is required to actually make the milk. Making milk is a bodily function that needs fuel. After I initially wrote this post, a reader studying for her lactation consultancy exams wrote in to tell me that the production efficiency (or the amount of energy needed to make milk) is 80% of the energy produced. I was able to find other studies that back up this number.
Therefore, the total calories that you burn by breastfeeding are the calories in the milk plus the energy required to produce the milk.
How Many Calories Does Pumping Burn? Breastfeeding Calorie Burn Calculation Formula
Here’s an example. If you pump 20 oz, you would multiply that by the 20 calories that is in the milk, and then divide that by .8 (the production efficiency) to get the total calories burned by breastfeeding (including the milk you make AND the energy you burned making the milk). So your total calorie burn from breastfeeding would be:
(20 oz * 20 calories)/0.8 = 500 total breastfeeding calories (400 calories from the breast milk itself; plus an additional 100 in energy to make the milk)
So just plug your number of ounces in the below breastfeeding calorie burn calculation formula:
(# of oz * 20)/0.8 = Total Breastfeeding Calories
Here’s the metric system version:
(# of ml * .68)/0.8 = Total Breastfeeding Calories
Does Pumping Burn the Same Amount of Calories as Nursing?
The only thing that matter is the amount of breast milk that is produced.
So, 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 more milk than your baby would otherwise eat.
Four Challenges Breastfeeding Moms Face When Losing Weight
There are some things that make postpartum weight loss different (and harder!) as compared to “normal” weight loss – especially when you are nursing or exclusively pumping. Here are the big ones.
Challenge #1: Hormones
New moms seem to fall into one of two categories when it comes to losing weight while breastfeeding*:
- Mom loses weight quickly and easily and can eat whatever she wants until she weans. (She may then gain some weight if she doesn’t adjust her intake appropriately.)
- Mom loses a decent amount of baby weight but holds onto an extra 5-10 pounds until she weans.
* This is based on my own experience, my friends’ experiences, and what I’ve learned spending way too much time reading parenting message boards.
Personally, I fell into the first category with my son and am in the second category with my daughter. Need I say that the first is better? If you’re in the first group, yay! If you’re in the second, there is not much that you can do except realize that this is not uncommon and the issue should hopefully resolve itself when you wean. You also might want to consider how much effort you want to put into losing the remaining baby weight given that your hormones are fighting you and that this is likely temporary.
Challenge #2: Raging Appetite
If you are pumping 25 ounces a milk a day, you are burning the same amount of extra calories as if you were running 5 miles every single day. You are going to be hungry!
Two things that I have done to combat this – first, make sure that you are eating enough calories. If you would normally eat, say, 1500 calories to lose weight, figure out how many breastfeeding calories you are burning and add that to the total that you eat every day. The second is to have a lot of easy, weight-loss friendly snacks on hand that work for you. My usual snack is a few spoonfuls of an enormous fruit salad that I make at the beginning of every week along with a Hershey’s Kiss. Between the bulk of the fruit and the fat from the Kiss, it’s reasonably filling.
Challenge #3: Sleep Deprivation
For years, studies have shown a link between weight gain and sleep deprivation, so the advice that doctors and weight loss gurus give people trying to lose weight is to sleep for eight consecutive hours a night. When you have a new baby, that’s obviously just not going to happen. (Unless you are really lucky!)
When you baby gets a little older, though, hopefully it will – and then getting a good night’s sleep is great advice to follow. Before that, though, what to do?
The issue with sleep and weight gain is that lack of sleep makes your body want more food. Junk food, to be specific. The good news is that, if you don’t give into the impulse to eat lots of high-calorie food, you will probably be fine – the lack of sleep on its own doesn’t seem to affect the calories in/calories out equation. However, if this is really hard for you, maybe just recognize that weight loss might be too difficult when you aren’t sleeping well and wait to start trying to lose weight until your baby is sleeping longer stretches.
Challenge #4: You Have a Baby and No Longer Have Any Free Time
It’s hard to get time to yourself when you are a new mama to a baby. I find this to be a weight loss challenge for two reasons. The obvious one is that you have less time to work out, which I’ll talk about in the next post.
The less obvious one, though, is that when you find yourself stressed, it’s harder to deal with it in the ways you might have pre-baby (taking a walk, taking a bath, going out with your friends) because you have an infant. It’s much easier to just eat something and feel better. (I have a lot of experience in eating my feelings – I think I have an extra stretch mark for every ultrasound I went to when I was pregnant with my son!) For me, the first step to dealing with this is recognizing what I’m doing. From there, you can come up with a plan that works for you to try not to eat due to stress.
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!
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.