Updated: Jan 14
Breastfeeding comes with many benefits for you and your baby. One of the most talked about benefits is that it *can* assist you in losing the weight you put on during pregnancy. Although breastfeeding doesn't automatically guarantee weight loss, there's no denying that producing breast milk uses a lot of energy (a.k.a. 'burns a lot of calories').
How Many Calories Does Breastfeeding Burn?
The amount of calories you need while breastfeeding depends on a few things:
Your basal metabolic rate (BMR) = how many calories you burn at rest (this depends mostly on your body weight, height, age and gender)
Your physical activity level (PAL) = how much you move throughout the day (not just exercise, but daily activities like washing dishes as well)
How much milk you produce (exclusively breastfeeding moms produce around 725 ml (24 to 25 oz) of breast milk per day, while partial breastfeeding moms produce less)
The energy density of your milk (there are around 65 calories in 100 ml of breast milk, or 19 to 20 calories per oz)
How much energy it takes for your body to produce milk (the metabolic processes involved in milk production)
It's complicated math, which is why I developed a calorie calculator down below to give you an estimate. However, please note that calorie calculators are always *just* estimators. Each of us is individual in how much energy we burn exactly. Some of us have a faster metabolism than others; some of us have a higher muscle mass, which also 'burns' more calories.
The amount of breast milk you produce while exclusively breastfeeding *one* baby is around 725 ml (24 to 25 ounces) per day, although this number can be higher if you pump in addition or breastfeed multiples. It can be lower if you supplement with formula or your baby has already started solid foods.
The energy density (= amount of calories) in your breast milk varies, too. It's mostly dependent on the fat concentration in your milk, which is highly variable. It changes throughout the day, within a feed and is different from mom to mom. However, a number of studies have estimated that the average calorie content of breast milk is around 65 calories per 100 ml, or 19 to 20 calories per ounce (source).
Taking all of these numbers and variables together, exclusive breastfeeding burns around 500 to 670 extra calories per day! That's about as many calories as you'd burn on a 45 minute run. While this may not sound like much, consider you're going on this 45 minute run EVERY SINGLE DAY!
How Many Calories do I Burn if I don't feed exclusively?
If you breastfeed, but not exclusively - that means, your baby is getting formula and/or solid foods in addition - you still burn extra calories. How many exactly depends, of course, on the amount of breast milk you still produce and the fat content of your milk. If you pump, you can get a good estimate of that. If you don't, use the following estimate:
If your baby drinks mostly breast milk with no more than 2 formula feeds per day or your baby has just started eating solid foods but still gets most of the energy from breast milk, estimate around 400 extra calories per day.
If your baby gets around half of its feeds from formula or solid foods, estimate around 250 extra calories per day.
These are just estimates, of course - there are many 'in-betweens'. Use these estimates as a 'guide', but if you gain or lose too much weight on these estimates, adjust your intake accordingly!
How can I lose weight without losing my milk supply?
As you may have heard, losing weight has a lot to do with how many calories you burn vs. how many calories you take in. Only if you are in a calorie deficit, will you lose weight.
However, it's not quite as simple as cutting calories to lose weight. As I've explained in my popular post "5 Reasons You are Not Losing Weight While Breastfeeding" post, our bodies have mechanisms in place which will keep us from losing weight if we cut calories too much or for too long.
This especially applies to the breastfeeding phase, during which hormonal changes keep us from losing too much weight. If we cut calories too much, our hunger signals go up, our metabolism can slow down, our body temperature can go down and, of course, our breast milk production can decrease also. All of these are ways our bodies can make up for our hard-earned calorie deficit.
But there is a way to lose weight while breastfeeding!
Follow these 6 simple rules for safe weight loss while breastfeeding:
Cut calories, but not too much - studies have shown that a moderate calorie restriction of 300 to 500 calories per day while breastfeeding should not affect your milk supply.
Include "eucaloric" days once or twice per week - these are days during which you 'up' your daily calorie intake to cover your expenditure in order to keep your metabolism and milk production from slowing down.
Focus on nutrient-dense foods - your body needs MORE nutrients while breastfeeding - not less! If we cut calories, we often also cut nutrients from our diet. Avoid this by focusing on nutrient-dense foods (as outlined in my meal plan for breastfeeding moms).
Make sure you are meeting your weekly requirements for some key nutrients for thyroid health, including Iodine, Selenium and Zinc. The thyroid controls the speed of our metabolism, and if it's lacking in nutrients, it can slow it down!
Don't forget to exercise (once you are cleared) - while breastfeeding, we tend to sit and lay more, and may ultimately lose muscle mass because of it. Focus on strength exercises rather than cardio because more muscle equals a faster metabolism. (After all, your cardio is already covered by breastfeeding!)
Reduce stress as much as possible - Stress hormones can stop your body in its weight loss tracks! Do something for yourself - every day - that makes you feel good! (I know this is probably the hardest, but a must!)
If weight loss doesn't happen, remember that these numbers are just estimates and you may have to experiment around a bit with how many calories YOUR body needs while breastfeeding.
Calorie Calculator for Pregnancy & Breastfeeding