How Many Calories Do I Need When Breastfeeding and Pumping?

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.

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